diff --git a/typo3/sysext/backend/Classes/Configuration/SiteTcaConfiguration.php b/typo3/sysext/backend/Classes/Configuration/SiteTcaConfiguration.php
index 1b32aeb37d1cdb657d275a8b8c8ce337ef150240..08f44e0c7a9873c2fbf122557988630f5f45451d 100644
--- a/typo3/sysext/backend/Classes/Configuration/SiteTcaConfiguration.php
+++ b/typo3/sysext/backend/Classes/Configuration/SiteTcaConfiguration.php
@@ -23,41 +23,42 @@ use TYPO3\CMS\Core\Utility\GeneralUtility;
 /**
  * Helper class for the backend "Sites" module
  *
- * Load Site configuration TCA from ext:*Configuration/SiteConfigurationTCA
- * and ext:*Configuration/SiteConfigurationTCA/Overrides
+ * Load Site configuration TCA from ext:*Configuration/SiteConfiguration
+ * and ext:*Configuration/SiteConfiguration/Overrides
  */
 class SiteTcaConfiguration
 {
     /**
      * Returns a "fake TCA" array that is syntactically identical to
-     * "normal" TCA, and just isn't available as $GLOBALS['TCA'].
+     * "normal" TCA, but is not available as $GLOBALS['TCA']. During
+     * configuration loading time, the target array is available as
+     * $GLOBALS['SiteConfiguration'] within the Overrides files.
+     *
+     * It is not possible to use ExtensionManagementUtility methods.
      *
      * @return array
      */
     public function getTca(): array
     {
-        // To allow casual ExtensionManagementUtility methods that works on $GLOBALS['TCA']
-        // to change our fake TCA, just kick original TCA, and reset to original at the end.
-        $originalTca = $GLOBALS['TCA'];
-        $GLOBALS['TCA'] = [];
+        $GLOBALS['SiteConfiguration'] = [];
         $activePackages = GeneralUtility::makeInstance(PackageManager::class)->getActivePackages();
-        // First load "full table" files from Configuration/SiteConfigurationTCA
+        // First load "full table" files from Configuration/SiteConfiguration
         $finder = new Finder();
         foreach ($activePackages as $package) {
             try {
-                $finder->files()->depth(0)->name('*.php')->in($package->getPackagePath() . 'Configuration/SiteConfigurationTCA');
+                $finder->files()->depth(0)->name('*.php')->in($package->getPackagePath() . 'Configuration/SiteConfiguration');
             } catch (\InvalidArgumentException $e) {
                 // No such directory in this package
                 continue;
             }
             foreach ($finder as $fileInfo) {
-                $GLOBALS['TCA'][substr($fileInfo->getBasename(), 0, -4)] = require $fileInfo->getPathname();
+                $GLOBALS['SiteConfiguration'][substr($fileInfo->getBasename(), 0, -4)] = require $fileInfo->getPathname();
             }
         }
-        // Execute override files from Configuration/TCA/Overrides
+        // Execute override files from Configuration/SiteConfiguration/Overrides
         foreach ($activePackages as $package) {
             try {
-                $finder->files()->depth(0)->name('*.php')->in($package->getPackagePath() . 'Configuration/SiteConfigurationTCA/Overrides');
+                $finder->files()->depth(0)->name('*.php')->in($package->getPackagePath() . 'Configuration/SiteConfiguration/Overrides');
             } catch (\InvalidArgumentException $e) {
                 // No such directory in this package
                 continue;
@@ -66,8 +67,8 @@ class SiteTcaConfiguration
                 require $fileInfo->getPathname();
             }
         }
-        $result = $GLOBALS['TCA'];
-        $GLOBALS['TCA'] = $originalTca;
+        $result = $GLOBALS['SiteConfiguration'];
+        unset($GLOBALS['SiteConfiguration']);
         return $result;
     }
 }
diff --git a/typo3/sysext/backend/Classes/Controller/SiteConfigurationController.php b/typo3/sysext/backend/Classes/Controller/SiteConfigurationController.php
index dc17e095bfebc1f09fcba881e6bd240a24306c88..f91fea916b97b95e33200e88556d28c108516d47 100644
--- a/typo3/sysext/backend/Classes/Controller/SiteConfigurationController.php
+++ b/typo3/sysext/backend/Classes/Controller/SiteConfigurationController.php
@@ -124,7 +124,7 @@ class SiteConfigurationController
     {
         $this->configureEditViewDocHeader();
 
-        // Put sys_site and friends TCA into global TCA
+        // Put site and friends TCA into global TCA
         // @todo: We might be able to get rid of that later
         $GLOBALS['TCA'] = array_merge($GLOBALS['TCA'], GeneralUtility::makeInstance(SiteTcaConfiguration::class)->getTca());
 
@@ -138,7 +138,7 @@ class SiteConfigurationController
 
         $defaultValues = [];
         if ($isNewConfig) {
-            $defaultValues['sys_site']['rootPageId'] = $pageUid;
+            $defaultValues['site']['rootPageId'] = $pageUid;
         }
 
         $allSites = $this->siteFinder->getAllSites();
@@ -152,7 +152,7 @@ class SiteConfigurationController
         $formDataGroup = GeneralUtility::makeInstance(SiteConfigurationDataGroup::class);
         $formDataCompiler = GeneralUtility::makeInstance(FormDataCompiler::class, $formDataGroup);
         $formDataCompilerInput = [
-            'tableName' => 'sys_site',
+            'tableName' => 'site',
             'vanillaUid' => $isNewConfig ? $pageUid : $allSites[$siteIdentifier]->getRootPageId(),
             'command' => $isNewConfig ? 'new' : 'edit',
             'returnUrl' => (string)$returnUrl,
@@ -186,7 +186,7 @@ class SiteConfigurationController
      */
     protected function saveAction(ServerRequestInterface $request): ResponseInterface
     {
-        // Put sys_site and friends TCA into global TCA
+        // Put site and friends TCA into global TCA
         // @todo: We might be able to get rid of that later
         $GLOBALS['TCA'] = array_merge($GLOBALS['TCA'], GeneralUtility::makeInstance(SiteTcaConfiguration::class)->getTca());
 
@@ -205,14 +205,14 @@ class SiteConfigurationController
             throw new \RuntimeException('Either save or save and close', 1520370364);
         }
 
-        if (!isset($parsedBody['data']['sys_site']) || !is_array($parsedBody['data']['sys_site'])) {
-            throw new \RuntimeException('No sys_site data or sys_site identifier given', 1521030950);
+        if (!isset($parsedBody['data']['site']) || !is_array($parsedBody['data']['site'])) {
+            throw new \RuntimeException('No site data or site identifier given', 1521030950);
         }
 
         $data = $parsedBody['data'];
         // This can be NEW123 for new records
-        $pageId = (int)key($data['sys_site']);
-        $sysSiteRow = current($data['sys_site']);
+        $pageId = (int)key($data['site']);
+        $sysSiteRow = current($data['site']);
         $siteIdentifier = $sysSiteRow['identifier'] ?? '';
 
         $isNewConfiguration = false;
@@ -236,20 +236,20 @@ class SiteConfigurationController
 
         try {
             $newSysSiteData = [];
-            // Hard set rootPageId: This is TCA readOnly and not transmitted by FormEngine, but is also the "uid" of the sys_site record
+            // Hard set rootPageId: This is TCA readOnly and not transmitted by FormEngine, but is also the "uid" of the site record
             $newSysSiteData['site']['rootPageId'] = $pageId;
             foreach ($sysSiteRow as $fieldName => $fieldValue) {
-                $type = $siteTca['sys_site']['columns'][$fieldName]['config']['type'];
+                $type = $siteTca['site']['columns'][$fieldName]['config']['type'];
                 if ($type === 'input') {
-                    $fieldValue = $this->validateAndProcessValue('sys_site', $fieldName, $fieldValue);
+                    $fieldValue = $this->validateAndProcessValue('site', $fieldName, $fieldValue);
                     $newSysSiteData['site'][$fieldName] = $fieldValue;
                 } elseif ($type === 'inline') {
                     $newSysSiteData['site'][$fieldName] = [];
                     $childRowIds = GeneralUtility::trimExplode(',', $fieldValue, true);
-                    if (!isset($siteTca['sys_site']['columns'][$fieldName]['config']['foreign_table'])) {
+                    if (!isset($siteTca['site']['columns'][$fieldName]['config']['foreign_table'])) {
                         throw new \RuntimeException('No foreign_table found for inline type', 1521555037);
                     }
-                    $foreignTable = $siteTca['sys_site']['columns'][$fieldName]['config']['foreign_table'];
+                    $foreignTable = $siteTca['site']['columns'][$fieldName]['config']['foreign_table'];
                     foreach ($childRowIds as $childRowId) {
                         $childRowData = [];
                         if (!isset($data[$foreignTable][$childRowId])) {
@@ -315,7 +315,7 @@ class SiteConfigurationController
     {
         $languageService = $this->getLanguageService();
         // Normal "eval" processing of field first
-        $identifier = $this->validateAndProcessValue('sys_site', 'identifier', $identifier);
+        $identifier = $this->validateAndProcessValue('site', 'identifier', $identifier);
         if ($isNew) {
             // Verify no other site with this identifier exists. If so, find a new unique name as
             // identifier and show a flash message the identifier has been adapted
diff --git a/typo3/sysext/backend/Classes/Controller/SiteInlineAjaxController.php b/typo3/sysext/backend/Classes/Controller/SiteInlineAjaxController.php
index d732aeeeed9577bc8e54199baf02cb7d25ed3226..6d8a46ea891313c7f880f6c081c0a6db85a8c4cf 100644
--- a/typo3/sysext/backend/Classes/Controller/SiteInlineAjaxController.php
+++ b/typo3/sysext/backend/Classes/Controller/SiteInlineAjaxController.php
@@ -81,8 +81,8 @@ class SiteInlineAjaxController extends AbstractFormEngineAjaxController
         $childTableName = $parentConfig['foreign_table'];
 
         $defaultDatabaseRow = [];
-        if ($childTableName === 'sys_site_language') {
-            // Feed new sys_site_language row with data from sys_language record if possible
+        if ($childTableName === 'site_language') {
+            // Feed new site_language row with data from sys_language record if possible
             if ($childChildUid > 0) {
                 $queryBuilder = GeneralUtility::makeInstance(ConnectionPool::class)->getQueryBuilderForTable('sys_language');
                 $queryBuilder->getRestrictions()->removeByType(HiddenRestriction::class);
diff --git a/typo3/sysext/backend/Classes/Form/FormDataProvider/SiteDatabaseEditRow.php b/typo3/sysext/backend/Classes/Form/FormDataProvider/SiteDatabaseEditRow.php
index b4f1a60558f2e2589409dcf14222904b991ca3bf..72f21af4fa60c9e288279e93d3c807e037517980 100644
--- a/typo3/sysext/backend/Classes/Form/FormDataProvider/SiteDatabaseEditRow.php
+++ b/typo3/sysext/backend/Classes/Form/FormDataProvider/SiteDatabaseEditRow.php
@@ -41,12 +41,12 @@ class SiteDatabaseEditRow implements FormDataProviderInterface
 
         $tableName = $result['tableName'];
         $siteFinder = GeneralUtility::makeInstance(SiteFinder::class);
-        if ($tableName === 'sys_site') {
+        if ($tableName === 'site') {
             $siteConfigurationForPageUid = (int)$result['vanillaUid'];
             $rowData = $siteFinder->getSiteByRootPageId($siteConfigurationForPageUid)->getConfiguration();
             $result['databaseRow']['uid'] = $rowData['rootPageId'];
             $result['databaseRow']['identifier'] = $result['customData']['siteIdentifier'];
-        } elseif ($tableName === 'sys_site_errorhandling' || $tableName === 'sys_site_language') {
+        } elseif ($tableName === 'site_errorhandling' || $tableName === 'site_language') {
             $siteConfigurationForPageUid = (int)($result['inlineTopMostParentUid'] ?? $result['inlineParentUid']);
             $rowData = $siteFinder->getSiteByRootPageId($siteConfigurationForPageUid)->getConfiguration();
             $parentFieldName = $result['inlineParentFieldName'];
diff --git a/typo3/sysext/backend/Classes/Form/FormDataProvider/SiteTcaInline.php b/typo3/sysext/backend/Classes/Form/FormDataProvider/SiteTcaInline.php
index c4cf7d380a04782332d00c83bcaaf91ca693b3ab..3f1903f414880903c879931e9de578048195d670 100644
--- a/typo3/sysext/backend/Classes/Form/FormDataProvider/SiteTcaInline.php
+++ b/typo3/sysext/backend/Classes/Form/FormDataProvider/SiteTcaInline.php
@@ -29,7 +29,7 @@ use TYPO3\CMS\Core\Utility\GeneralUtility;
 /**
  * Special data provider for the sites configuration module.
  *
- * Handle inline children of 'sys_site"
+ * Handle inline children of 'site'
  */
 class SiteTcaInline extends AbstractDatabaseRecordProvider implements FormDataProviderInterface
 {
@@ -47,7 +47,7 @@ class SiteTcaInline extends AbstractDatabaseRecordProvider implements FormDataPr
                 continue;
             }
             $childTableName = $fieldConfig['config']['foreign_table'];
-            if ($childTableName !== 'sys_site_errorhandling' && $childTableName !== 'sys_site_language') {
+            if ($childTableName !== 'site_errorhandling' && $childTableName !== 'site_language') {
                 throw new \RuntimeException('Inline relation to other tables not implemented', 1522494737);
             }
             $result['processedTca']['columns'][$fieldName]['children'] = [];
@@ -122,9 +122,9 @@ class SiteTcaInline extends AbstractDatabaseRecordProvider implements FormDataPr
             }
         }
 
-        // If we are dealing with sys_site_language, we *always* force a relation to sys_language "0"
+        // If we are dealing with site_language, we *always* force a relation to sys_language "0"
         $foreignTable = $result['processedTca']['columns'][$fieldName]['config']['foreign_table'];
-        if ($foreignTable === 'sys_site_language' && $result['command'] === 'new') {
+        if ($foreignTable === 'site_language' && $result['command'] === 'new') {
             // If new, just add a new default child
             $child = $this->compileDefaultSysSiteLanguageChild($result, $fieldName);
             $connectedUids[] = $child['databaseRow']['uid'];
@@ -141,8 +141,8 @@ class SiteTcaInline extends AbstractDatabaseRecordProvider implements FormDataPr
             }
         }
 
-        // If we are dealing with sys_site_language, we *always* force a relation to sys_language "0"
-        if ($foreignTable === 'sys_site_language' && $result['command'] === 'edit') {
+        // If we are dealing with ite_language, we *always* force a relation to sys_language "0"
+        if ($foreignTable === 'site_language' && $result['command'] === 'edit') {
             // If edit, find out if a child using sys_language "0" exists, else add it on top
             $defaultSysSiteLanguageChildFound = false;
             foreach ($result['processedTca']['columns'][$fieldName]['children'] as $child) {
@@ -264,7 +264,7 @@ class SiteTcaInline extends AbstractDatabaseRecordProvider implements FormDataPr
     }
 
     /**
-     * Compile default sys_site_language child using sys_language uid "0"
+     * Compile default site_language child using sys_language uid "0"
      *
      * @param array $result
      * @param string $parentFieldName
@@ -280,7 +280,7 @@ class SiteTcaInline extends AbstractDatabaseRecordProvider implements FormDataPr
         $formDataCompiler = GeneralUtility::makeInstance(FormDataCompiler::class, $formDataGroup);
         $formDataCompilerInput = [
             'command' => 'new',
-            'tableName' => 'sys_site_language',
+            'tableName' => 'site_language',
             'vanillaUid' => $result['inlineFirstPid'],
             'returnUrl' => $result['returnUrl'],
             'isInlineChild' => true,
diff --git a/typo3/sysext/backend/Classes/Form/FormDataProvider/SiteTcaSelectItems.php b/typo3/sysext/backend/Classes/Form/FormDataProvider/SiteTcaSelectItems.php
index 548efdf02316ea4d8cc71aaf02938fa9100b388f..6b511f7f3277d8ab09e83aad7d651c98c5d98447 100644
--- a/typo3/sysext/backend/Classes/Form/FormDataProvider/SiteTcaSelectItems.php
+++ b/typo3/sysext/backend/Classes/Form/FormDataProvider/SiteTcaSelectItems.php
@@ -29,7 +29,7 @@ class SiteTcaSelectItems implements FormDataProviderInterface
 {
     /**
      * Resolve select items for
-     * * 'sys_site_language' -> 'typo3language'
+     * * 'site_language' -> 'typo3language'
      *
      * @param array $result
      * @return array
@@ -38,7 +38,7 @@ class SiteTcaSelectItems implements FormDataProviderInterface
     public function addData(array $result): array
     {
         $table = $result['tableName'];
-        if ($table !== 'sys_site_language') {
+        if ($table !== 'site_language') {
             return $result;
         }
 
diff --git a/typo3/sysext/backend/Configuration/SiteConfigurationTCA/sys_site.php b/typo3/sysext/backend/Configuration/SiteConfiguration/site.php
similarity index 83%
rename from typo3/sysext/backend/Configuration/SiteConfigurationTCA/sys_site.php
rename to typo3/sysext/backend/Configuration/SiteConfiguration/site.php
index 834cfb3f6019697cb5ea992768883de6d4f827d7..ab4ae85627543f44fda3a2dcb6acc83b611feec5 100644
--- a/typo3/sysext/backend/Configuration/SiteConfigurationTCA/sys_site.php
+++ b/typo3/sysext/backend/Configuration/SiteConfiguration/site.php
@@ -3,14 +3,14 @@
 return [
     'ctrl' => [
         'label' => 'identifier',
-        'title' => 'LLL:EXT:backend/Resources/Private/Language/locallang_siteconfiguration_tca.xlf:sys_site.ctrl.title',
+        'title' => 'LLL:EXT:backend/Resources/Private/Language/locallang_siteconfiguration_tca.xlf:site.ctrl.title',
         'typeicon_classes' => [
             'default' => 'mimetypes-x-content-domain',
         ],
     ],
     'columns' => [
         'identifier' => [
-            'label' => 'LLL:EXT:backend/Resources/Private/Language/locallang_siteconfiguration_tca.xlf:sys_site.identifier',
+            'label' => 'LLL:EXT:backend/Resources/Private/Language/locallang_siteconfiguration_tca.xlf:site.identifier',
             'config' => [
                 'type' => 'input',
                 'size' => 35,
@@ -26,7 +26,7 @@ return [
             ],
         ],
         'rootPageId' => [
-            'label' => 'LLL:EXT:backend/Resources/Private/Language/locallang_siteconfiguration_tca.xlf:sys_site.rootPageId',
+            'label' => 'LLL:EXT:backend/Resources/Private/Language/locallang_siteconfiguration_tca.xlf:site.rootPageId',
             'config' => [
                 'type' => 'select',
                 'readOnly' => true,
@@ -41,7 +41,7 @@ return [
             ],
         ],
         'base' => [
-            'label' => 'LLL:EXT:backend/Resources/Private/Language/locallang_siteconfiguration_tca.xlf:sys_site.base',
+            'label' => 'LLL:EXT:backend/Resources/Private/Language/locallang_siteconfiguration_tca.xlf:site.base',
             'config' => [
                 'type' => 'input',
                 'eval' => 'required',
@@ -53,10 +53,10 @@ return [
             ],
         ],
         'languages' => [
-            'label' => 'LLL:EXT:backend/Resources/Private/Language/locallang_siteconfiguration_tca.xlf:sys_site.languages',
+            'label' => 'LLL:EXT:backend/Resources/Private/Language/locallang_siteconfiguration_tca.xlf:site.languages',
             'config' => [
                 'type' => 'inline',
-                'foreign_table' => 'sys_site_language',
+                'foreign_table' => 'site_language',
                 'foreign_selector' => 'languageId',
                 'foreign_unique' => 'languageId',
                 'size' => 4,
@@ -69,10 +69,10 @@ return [
             ],
         ],
         'errorHandling' => [
-            'label' => 'LLL:EXT:backend/Resources/Private/Language/locallang_siteconfiguration_tca.xlf:sys_site.errorHandling',
+            'label' => 'LLL:EXT:backend/Resources/Private/Language/locallang_siteconfiguration_tca.xlf:site.errorHandling',
             'config' => [
                 'type' => 'inline',
-                'foreign_table' => 'sys_site_errorhandling',
+                'foreign_table' => 'site_errorhandling',
                 'appearance' => [
                     'enabledControls' => [
                         'info' => false,
@@ -84,8 +84,8 @@ return [
     'types' => [
         '0' => [
             'showitem' => 'identifier, rootPageId, base,
-                --div--;LLL:EXT:backend/Resources/Private/Language/locallang_siteconfiguration_tca.xlf:sys_site.tab.languages, languages,
-                --div--;LLL:EXT:backend/Resources/Private/Language/locallang_siteconfiguration_tca.xlf:sys_site.tab.errorHandling, errorHandling',
+                --div--;LLL:EXT:backend/Resources/Private/Language/locallang_siteconfiguration_tca.xlf:site.tab.languages, languages,
+                --div--;LLL:EXT:backend/Resources/Private/Language/locallang_siteconfiguration_tca.xlf:site.tab.errorHandling, errorHandling',
         ],
     ],
 ];
diff --git a/typo3/sysext/backend/Configuration/SiteConfigurationTCA/sys_site_errorhandling.php b/typo3/sysext/backend/Configuration/SiteConfiguration/site_errorhandling.php
similarity index 81%
rename from typo3/sysext/backend/Configuration/SiteConfigurationTCA/sys_site_errorhandling.php
rename to typo3/sysext/backend/Configuration/SiteConfiguration/site_errorhandling.php
index c90677310a2e908093b9eb9a69f24d426669d7c0..71e9ed5120ec3dcbb76597c73b8c98dc75f6fbd8 100644
--- a/typo3/sysext/backend/Configuration/SiteConfigurationTCA/sys_site_errorhandling.php
+++ b/typo3/sysext/backend/Configuration/SiteConfiguration/site_errorhandling.php
@@ -3,7 +3,7 @@
 return [
     'ctrl' => [
         'label' => 'errorCode',
-        'title' => 'LLL:EXT:backend/Resources/Private/Language/locallang_siteconfiguration_tca.xlf:sys_site_errorhandling.ctrl.title',
+        'title' => 'LLL:EXT:backend/Resources/Private/Language/locallang_siteconfiguration_tca.xlf:site_errorhandling.ctrl.title',
         'type' => 'errorHandler',
         'typeicon_column' => 'errorHandler',
         'typeicon_classes' => [
@@ -15,7 +15,7 @@ return [
     ],
     'columns' => [
         'errorCode' => [
-            'label' => 'LLL:EXT:backend/Resources/Private/Language/locallang_siteconfiguration_tca.xlf:sys_site_errorhandling.errorCode',
+            'label' => 'LLL:EXT:backend/Resources/Private/Language/locallang_siteconfiguration_tca.xlf:site_errorhandling.errorCode',
             'config' => [
                 'type' => 'input',
                 'eval' => 'required, trim, int',
@@ -27,12 +27,12 @@ return [
                 'valuePicker' => [
                     'mode' => '',
                     'items' => [
-                        ['LLL:EXT:backend/Resources/Private/Language/locallang_siteconfiguration_tca.xlf:sys_site_errorhandling.errorCode.404', '404'],
-                        ['LLL:EXT:backend/Resources/Private/Language/locallang_siteconfiguration_tca.xlf:sys_site_errorhandling.errorCode.403', '403'],
-                        ['LLL:EXT:backend/Resources/Private/Language/locallang_siteconfiguration_tca.xlf:sys_site_errorhandling.errorCode.401', '401'],
-                        ['LLL:EXT:backend/Resources/Private/Language/locallang_siteconfiguration_tca.xlf:sys_site_errorhandling.errorCode.500', '500'],
-                        ['LLL:EXT:backend/Resources/Private/Language/locallang_siteconfiguration_tca.xlf:sys_site_errorhandling.errorCode.503', '503'],
-                        ['LLL:EXT:backend/Resources/Private/Language/locallang_siteconfiguration_tca.xlf:sys_site_errorhandling.errorCode.0', '0'],
+                        ['LLL:EXT:backend/Resources/Private/Language/locallang_siteconfiguration_tca.xlf:site_errorhandling.errorCode.404', '404'],
+                        ['LLL:EXT:backend/Resources/Private/Language/locallang_siteconfiguration_tca.xlf:site_errorhandling.errorCode.403', '403'],
+                        ['LLL:EXT:backend/Resources/Private/Language/locallang_siteconfiguration_tca.xlf:site_errorhandling.errorCode.401', '401'],
+                        ['LLL:EXT:backend/Resources/Private/Language/locallang_siteconfiguration_tca.xlf:site_errorhandling.errorCode.500', '500'],
+                        ['LLL:EXT:backend/Resources/Private/Language/locallang_siteconfiguration_tca.xlf:site_errorhandling.errorCode.503', '503'],
+                        ['LLL:EXT:backend/Resources/Private/Language/locallang_siteconfiguration_tca.xlf:site_errorhandling.errorCode.0', '0'],
                     ],
                 ],
                 'fieldInformation' => [
@@ -43,7 +43,7 @@ return [
             ],
         ],
         'errorHandler' => [
-            'label' => 'LLL:EXT:backend/Resources/Private/Language/locallang_siteconfiguration_tca.xlf:sys_site_errorhandling.errorHandler',
+            'label' => 'LLL:EXT:backend/Resources/Private/Language/locallang_siteconfiguration_tca.xlf:site_errorhandling.errorHandler',
             'config' => [
                 'type' => 'select',
                 'renderType' => 'selectSingle',
@@ -61,7 +61,7 @@ return [
             ],
         ],
         'errorFluidTemplate' => [
-            'label' => 'LLL:EXT:backend/Resources/Private/Language/locallang_siteconfiguration_tca.xlf:sys_site_errorhandling.errorFluidTemplate',
+            'label' => 'LLL:EXT:backend/Resources/Private/Language/locallang_siteconfiguration_tca.xlf:site_errorhandling.errorFluidTemplate',
             'config' => [
                 'type' => 'input',
                 'eval' => 'required',
@@ -73,7 +73,7 @@ return [
             ],
         ],
         'errorFluidTemplatesRootPath' => [
-            'label' => 'LLL:EXT:backend/Resources/Private/Language/locallang_siteconfiguration_tca.xlf:sys_site_errorhandling.errorFluidTemplatesRootPath',
+            'label' => 'LLL:EXT:backend/Resources/Private/Language/locallang_siteconfiguration_tca.xlf:site_errorhandling.errorFluidTemplatesRootPath',
             'config' => [
                 'type' => 'input',
                 'fieldInformation' => [
@@ -84,7 +84,7 @@ return [
             ],
         ],
         'errorFluidLayoutsRootPath' => [
-            'label' => 'LLL:EXT:backend/Resources/Private/Language/locallang_siteconfiguration_tca.xlf:sys_site_errorhandling.errorFluidLayoutsRootPath',
+            'label' => 'LLL:EXT:backend/Resources/Private/Language/locallang_siteconfiguration_tca.xlf:site_errorhandling.errorFluidLayoutsRootPath',
             'config' => [
                 'type' => 'input',
                 'fieldInformation' => [
@@ -95,7 +95,7 @@ return [
             ],
         ],
         'errorFluidPartialsRootPath' => [
-            'label' => 'LLL:EXT:backend/Resources/Private/Language/locallang_siteconfiguration_tca.xlf:sys_site_errorhandling.errorFluidPartialsRootPath',
+            'label' => 'LLL:EXT:backend/Resources/Private/Language/locallang_siteconfiguration_tca.xlf:site_errorhandling.errorFluidPartialsRootPath',
             'config' => [
                 'type' => 'input',
                 'fieldInformation' => [
@@ -106,7 +106,7 @@ return [
             ],
         ],
         'errorContentSource' => [
-            'label' => 'LLL:EXT:backend/Resources/Private/Language/locallang_siteconfiguration_tca.xlf:sys_site_errorhandling.errorContentSource',
+            'label' => 'LLL:EXT:backend/Resources/Private/Language/locallang_siteconfiguration_tca.xlf:site_errorhandling.errorContentSource',
             'config' => [
                 'type' => 'input',
                 'renderType' => 'inputLink',
@@ -126,7 +126,7 @@ return [
             ],
         ],
         'errorPhpClassFQCN' => [
-            'label' => 'LLL:EXT:backend/Resources/Private/Language/locallang_siteconfiguration_tca.xlf:sys_site_errorhandling.errorPhpClassFQCN',
+            'label' => 'LLL:EXT:backend/Resources/Private/Language/locallang_siteconfiguration_tca.xlf:site_errorhandling.errorPhpClassFQCN',
             'config' => [
                 'type' => 'input',
                 'eval' => 'required',
@@ -144,7 +144,7 @@ return [
         ],
         'Fluid' => [
             'showitem' => 'errorCode, errorHandler, errorFluidTemplate,
-                           --div--;LLL:EXT:backend/Resources/Private/Language/locallang_siteconfiguration_tca.xlf:sys_site_errorhandling.tab.rootpaths,
+                           --div--;LLL:EXT:backend/Resources/Private/Language/locallang_siteconfiguration_tca.xlf:site_errorhandling.tab.rootpaths,
                            errorFluidTemplatesRootPath, errorFluidLayoutsRootPath, errorFluidPartialsRootPath',
         ],
         'Page' => [
diff --git a/typo3/sysext/backend/Configuration/SiteConfigurationTCA/sys_site_language.php b/typo3/sysext/backend/Configuration/SiteConfiguration/site_language.php
similarity index 95%
rename from typo3/sysext/backend/Configuration/SiteConfigurationTCA/sys_site_language.php
rename to typo3/sysext/backend/Configuration/SiteConfiguration/site_language.php
index db157ee0a66d94c2073839e51b57600f87667cc2..28caf8fda939c4bb3bd6a1b4a5413a7ca5453b26 100644
--- a/typo3/sysext/backend/Configuration/SiteConfigurationTCA/sys_site_language.php
+++ b/typo3/sysext/backend/Configuration/SiteConfiguration/site_language.php
@@ -3,14 +3,14 @@
 return [
     'ctrl' => [
         'label' => 'languageId',
-        'title' => 'LLL:EXT:backend/Resources/Private/Language/locallang_siteconfiguration_tca.xlf:sys_site_language.ctrl.title',
+        'title' => 'LLL:EXT:backend/Resources/Private/Language/locallang_siteconfiguration_tca.xlf:site_language.ctrl.title',
         'typeicon_classes' => [
             'default' => 'mimetypes-x-content-domain',
         ],
     ],
     'columns' => [
         'languageId' => [
-            'label' => 'LLL:EXT:backend/Resources/Private/Language/locallang_siteconfiguration_tca.xlf:sys_site_language.language',
+            'label' => 'LLL:EXT:backend/Resources/Private/Language/locallang_siteconfiguration_tca.xlf:site_language.language',
             'config' => [
                 'type' => 'select',
                 'renderType' => 'selectSingle',
@@ -29,7 +29,7 @@ return [
             ],
         ],
         'title' => [
-            'label' => 'LLL:EXT:backend/Resources/Private/Language/locallang_siteconfiguration_tca.xlf:sys_site_language.title',
+            'label' => 'LLL:EXT:backend/Resources/Private/Language/locallang_siteconfiguration_tca.xlf:site_language.title',
             'config' => [
                 'type' => 'input',
                 'size' => 10,
@@ -43,7 +43,7 @@ return [
             ],
         ],
         'navigationTitle' => [
-            'label' => 'LLL:EXT:backend/Resources/Private/Language/locallang_siteconfiguration_tca.xlf:sys_site_language.navigationTitle',
+            'label' => 'LLL:EXT:backend/Resources/Private/Language/locallang_siteconfiguration_tca.xlf:site_language.navigationTitle',
             'config' => [
                 'type' => 'input',
                 'size' => 10,
@@ -56,7 +56,7 @@ return [
             ],
         ],
         'base' => [
-            'label' => 'LLL:EXT:backend/Resources/Private/Language/locallang_siteconfiguration_tca.xlf:sys_site_language.base',
+            'label' => 'LLL:EXT:backend/Resources/Private/Language/locallang_siteconfiguration_tca.xlf:site_language.base',
             'config' => [
                 'type' => 'input',
                 'eval' => 'required',
@@ -69,7 +69,7 @@ return [
             ],
         ],
         'locale' => [
-            'label' => 'LLL:EXT:backend/Resources/Private/Language/locallang_siteconfiguration_tca.xlf:sys_site_language.locale',
+            'label' => 'LLL:EXT:backend/Resources/Private/Language/locallang_siteconfiguration_tca.xlf:site_language.locale',
             'config' => [
                 'type' => 'input',
                 'eval' => 'required',
@@ -82,7 +82,7 @@ return [
             ],
         ],
         'iso-639-1' => [
-            'label' => 'LLL:EXT:backend/Resources/Private/Language/locallang_siteconfiguration_tca.xlf:sys_site_language.iso-639-1',
+            'label' => 'LLL:EXT:backend/Resources/Private/Language/locallang_siteconfiguration_tca.xlf:site_language.iso-639-1',
             'config' => [
                 'type' => 'select',
                 'renderType' => 'selectSingle',
@@ -96,7 +96,7 @@ return [
             ],
         ],
         'hreflang' => [
-            'label' => 'LLL:EXT:backend/Resources/Private/Language/locallang_siteconfiguration_tca.xlf:sys_site_language.hreflang',
+            'label' => 'LLL:EXT:backend/Resources/Private/Language/locallang_siteconfiguration_tca.xlf:site_language.hreflang',
             'config' => [
                 'type' => 'input',
                 'placeholder' => 'en-US',
@@ -108,7 +108,7 @@ return [
             ],
         ],
         'direction' => [
-            'label' => 'LLL:EXT:backend/Resources/Private/Language/locallang_siteconfiguration_tca.xlf:sys_site_language.direction',
+            'label' => 'LLL:EXT:backend/Resources/Private/Language/locallang_siteconfiguration_tca.xlf:site_language.direction',
             'config' => [
                 'type' => 'select',
                 'renderType' => 'selectSingle',
@@ -125,7 +125,7 @@ return [
             ],
         ],
         'typo3Language' => [
-            'label' => 'LLL:EXT:backend/Resources/Private/Language/locallang_siteconfiguration_tca.xlf:sys_site_language.typo3Language',
+            'label' => 'LLL:EXT:backend/Resources/Private/Language/locallang_siteconfiguration_tca.xlf:site_language.typo3Language',
             'config' => [
                 'type' => 'select',
                 'renderType' => 'selectSingle',
@@ -140,7 +140,7 @@ return [
             ],
         ],
         'flag' => [
-            'label' => 'LLL:EXT:backend/Resources/Private/Language/locallang_siteconfiguration_tca.xlf:sys_site_language.flag',
+            'label' => 'LLL:EXT:backend/Resources/Private/Language/locallang_siteconfiguration_tca.xlf:site_language.flag',
             'config' => [
                 'type' => 'select',
                 'renderType' => 'selectSingle',
@@ -412,7 +412,7 @@ return [
             ],
         ],
         'fallbackType' => [
-            'label' => 'LLL:EXT:backend/Resources/Private/Language/locallang_siteconfiguration_tca.xlf:sys_site_language.fallbackType',
+            'label' => 'LLL:EXT:backend/Resources/Private/Language/locallang_siteconfiguration_tca.xlf:site_language.fallbackType',
             'displayCond' => 'FIELD:languageId:>:0',
             'onChange' => 'reload',
             'config' => [
@@ -430,7 +430,7 @@ return [
             ],
         ],
         'fallbacks' => [
-            'label' => 'LLL:EXT:backend/Resources/Private/Language/locallang_siteconfiguration_tca.xlf:sys_site_language.fallbacks',
+            'label' => 'LLL:EXT:backend/Resources/Private/Language/locallang_siteconfiguration_tca.xlf:site_language.fallbacks',
             'displayCond' => 'FIELD:fallbackType:=:fallback',
             'config' => [
                 'type' => 'select',
diff --git a/typo3/sysext/backend/Resources/Private/Language/locallang_siteconfiguration_tca.xlf b/typo3/sysext/backend/Resources/Private/Language/locallang_siteconfiguration_tca.xlf
index f3a5fd2a068dc6524e183e2572eda76c0d439305..a99d4ca776147c0157f6f7d9040044856adb0457 100644
--- a/typo3/sysext/backend/Resources/Private/Language/locallang_siteconfiguration_tca.xlf
+++ b/typo3/sysext/backend/Resources/Private/Language/locallang_siteconfiguration_tca.xlf
@@ -3,117 +3,117 @@
 	<file t3:id="1522785604" source-language="en" datatype="plaintext" original="messages" date="2018-02-27T22:22:32Z" product-name="backend">
 		<header/>
 		<body>
-			<trans-unit id="sys_site.ctrl.title">
+			<trans-unit id="site.ctrl.title">
 				<source>Site Configuration</source>
 			</trans-unit>
-			<trans-unit id="sys_site.identifier">
+			<trans-unit id="site.identifier">
 				<source>Site Identifier</source>
 			</trans-unit>
-			<trans-unit id="sys_site.rootPageId">
+			<trans-unit id="site.rootPageId">
 				<source>Root Page ID (You must create a page with a site root flag)</source>
 			</trans-unit>
-			<trans-unit id="sys_site.base">
+			<trans-unit id="site.base">
 				<source>Entry point (can be https://www.mydomain/ or just /, if it is just / you can not rely on TYPO3 creating full URLs)</source>
 			</trans-unit>
-			<trans-unit id="sys_site.languages">
+			<trans-unit id="site.languages">
 				<source>Available Languages for this site</source>
 			</trans-unit>
-			<trans-unit id="sys_site.errorHandling">
+			<trans-unit id="site.errorHandling">
 				<source>Error Handling</source>
 			</trans-unit>
-			<trans-unit id="sys_site.tab.languages">
+			<trans-unit id="site.tab.languages">
 				<source>Languages</source>
 			</trans-unit>
-			<trans-unit id="sys_site.tab.errorHandling">
+			<trans-unit id="site.tab.errorHandling">
 				<source>Error Handling</source>
 			</trans-unit>
 
-			<trans-unit id="sys_site_language.ctrl.title">
+			<trans-unit id="site_language.ctrl.title">
 				<source>Language Configuration for a Site</source>
 			</trans-unit>
-			<trans-unit id="sys_site_language.language">
+			<trans-unit id="site_language.language">
 				<source>Language</source>
 			</trans-unit>
-			<trans-unit id="sys_site_language.title">
+			<trans-unit id="site_language.title">
 				<source>Language title (e.g. "English")</source>
 			</trans-unit>
-			<trans-unit id="sys_site_language.navigationTitle">
+			<trans-unit id="site_language.navigationTitle">
 				<source>Navigation title (e.g. "English", "Deutsch", "Français")</source>
 			</trans-unit>
-			<trans-unit id="sys_site_language.base">
+			<trans-unit id="site_language.base">
 				<source>Entry point (either https://www.mydomain.fr/ or /fr/)</source>
 			</trans-unit>
-			<trans-unit id="sys_site_language.locale">
+			<trans-unit id="site_language.locale">
 				<source>Language locale</source>
 			</trans-unit>
-			<trans-unit id="sys_site_language.iso-639-1">
+			<trans-unit id="site_language.iso-639-1">
 				<source>Two letter ISO code</source>
 			</trans-unit>
-			<trans-unit id="sys_site_language.hreflang">
+			<trans-unit id="site_language.hreflang">
 				<source>Language tag defined by RFC 1766 / 3066 for "lang" and "hreflang" attributes</source>
 			</trans-unit>
-			<trans-unit id="sys_site_language.direction">
+			<trans-unit id="site_language.direction">
 				<source>Language direction for "dir" attribute</source>
 			</trans-unit>
-			<trans-unit id="sys_site_language.typo3Language">
+			<trans-unit id="site_language.typo3Language">
 				<source>Language key for XLF files</source>
 			</trans-unit>
-			<trans-unit id="sys_site_language.flag">
+			<trans-unit id="site_language.flag">
 				<source>Select flag icon</source>
 			</trans-unit>
-			<trans-unit id="sys_site_language.fallbackType">
+			<trans-unit id="site_language.fallbackType">
 				<source>Fallback type</source>
 			</trans-unit>
-			<trans-unit id="sys_site_language.fallbacks">
+			<trans-unit id="site_language.fallbacks">
 				<source>Fallback to other language(s) - order is important!</source>
 			</trans-unit>
 
-			<trans-unit id="sys_site_errorhandling.ctrl.title">
+			<trans-unit id="site_errorhandling.ctrl.title">
 				<source>Error Handling</source>
 			</trans-unit>
-			<trans-unit id="sys_site_errorhandling.tab.rootpaths">
+			<trans-unit id="site_errorhandling.tab.rootpaths">
 				<source>Root Paths (optional)</source>
 			</trans-unit>
-			<trans-unit id="sys_site_errorhandling.errorCode">
+			<trans-unit id="site_errorhandling.errorCode">
 				<source>Error Status Code</source>
 			</trans-unit>
-			<trans-unit id="sys_site_errorhandling.errorCode.404">
+			<trans-unit id="site_errorhandling.errorCode.404">
 				<source>404 (Page not found)</source>
 			</trans-unit>
-			<trans-unit id="sys_site_errorhandling.errorCode.403">
+			<trans-unit id="site_errorhandling.errorCode.403">
 				<source>403 (Forbidden)</source>
 			</trans-unit>
-			<trans-unit id="sys_site_errorhandling.errorCode.401">
+			<trans-unit id="site_errorhandling.errorCode.401">
 				<source>401 (Unauthorized)</source>
 			</trans-unit>
-			<trans-unit id="sys_site_errorhandling.errorCode.500">
+			<trans-unit id="site_errorhandling.errorCode.500">
 				<source>500 (Internal Server Error)</source>
 			</trans-unit>
-			<trans-unit id="sys_site_errorhandling.errorCode.503">
+			<trans-unit id="site_errorhandling.errorCode.503">
 				<source>503 (Service Unavailable)</source>
 			</trans-unit>
-			<trans-unit id="sys_site_errorhandling.errorCode.0">
+			<trans-unit id="site_errorhandling.errorCode.0">
 				<source>any error not defined otherwise</source>
 			</trans-unit>
-			<trans-unit id="sys_site_errorhandling.errorHandler">
+			<trans-unit id="site_errorhandling.errorHandler">
 				<source>How to handle errors</source>
 			</trans-unit>
-			<trans-unit id="sys_site_errorhandling.errorFluidTemplate">
+			<trans-unit id="site_errorhandling.errorFluidTemplate">
 				<source>Fluid Template File</source>
 			</trans-unit>
-			<trans-unit id="sys_site_errorhandling.errorFluidTemplatesRootPath">
+			<trans-unit id="site_errorhandling.errorFluidTemplatesRootPath">
 				<source>Fluid Templates Root Path</source>
 			</trans-unit>
-			<trans-unit id="sys_site_errorhandling.errorFluidLayoutsRootPath">
+			<trans-unit id="site_errorhandling.errorFluidLayoutsRootPath">
 				<source>Fluid Layouts Root Path</source>
 			</trans-unit>
-			<trans-unit id="sys_site_errorhandling.errorFluidPartialsRootPath">
+			<trans-unit id="site_errorhandling.errorFluidPartialsRootPath">
 				<source>Fluid Partials Root Path</source>
 			</trans-unit>
-			<trans-unit id="sys_site_errorhandling.errorContentSource">
+			<trans-unit id="site_errorhandling.errorContentSource">
 				<source>Show Content From Page</source>
 			</trans-unit>
-			<trans-unit id="sys_site_errorhandling.errorPhpClassFQCN">
+			<trans-unit id="site_errorhandling.errorPhpClassFQCN">
 				<source>ErrorHandler Class Target (FQCN)</source>
 			</trans-unit>
 		</body>
diff --git a/typo3/sysext/backend/Resources/Private/Language/siteconfiguration_fieldinformation.xlf b/typo3/sysext/backend/Resources/Private/Language/siteconfiguration_fieldinformation.xlf
index 4f3ae66cf59fe89c29ef27f020a92092e62a19a2..19bc4f57615cf4bb8201d81542ad600eaaf17e01 100644
--- a/typo3/sysext/backend/Resources/Private/Language/siteconfiguration_fieldinformation.xlf
+++ b/typo3/sysext/backend/Resources/Private/Language/siteconfiguration_fieldinformation.xlf
@@ -3,28 +3,28 @@
 	<file t3:id="1522923345" source-language="en" datatype="plaintext" original="messages" date="2015-01-02T11:16:11Z" product-name="backend">
 		<header/>
 		<body>
-			<trans-unit id="sys_site.identifier">
+			<trans-unit id="site.identifier">
 				<source>This name will be used to create the configuration directory. Mind the recommendations for directory names (only a-z,0-9,_,-) and make it unique.</source>
 			</trans-unit>
-			<trans-unit id="sys_site.base">
+			<trans-unit id="site.base">
 				<source>Main URL to call the frontend in default language.</source>
 			</trans-unit>
-			<trans-unit id="sys_site_language.base">
+			<trans-unit id="site_language.base">
 				<source>use / to use keep the main URL as configured at field Entry Point. Add language specific suffixes to use those, or configure complete URLs for independent domains.</source>
 			</trans-unit>
-			<trans-unit id="sys_site_language.locale">
+			<trans-unit id="site_language.locale">
 				<source>should be something like de_DE or en_US.UTF-8</source>
 			</trans-unit>
-			<trans-unit id="sys_site_language.typo3Language">
+			<trans-unit id="site_language.typo3Language">
 				<source>Select the language to be used from translation files. Keep default if no translation files are available.</source>
 			</trans-unit>
-			<trans-unit id="sys_site_errorhandling.errorCode">
+			<trans-unit id="site_errorhandling.errorCode">
 				<source>make sure to have at least 0 (not defined otherwise) configured in order to serve helpful error messages to your visitors.</source>
 			</trans-unit>
-			<trans-unit id="sys_site_errorhandling.errorFluidTemplate">
+			<trans-unit id="site_errorhandling.errorFluidTemplate">
 				<source>absolute or relative path (from site root) to fluid template file</source>
 			</trans-unit>
-			<trans-unit id="sys_site_errorhandling.errorPhpClassFQCN">
+			<trans-unit id="site_errorhandling.errorPhpClassFQCN">
 				<source>PHP class full qualified name that serves the error page.</source>
 			</trans-unit>
 		</body>
diff --git a/typo3/sysext/backend/Tests/Unit/Form/FormDataProvider/SiteDatabaseEditRowTest.php b/typo3/sysext/backend/Tests/Unit/Form/FormDataProvider/SiteDatabaseEditRowTest.php
index b01f82973bdaec15ac1e1815e6b126dd775bb797..2cc100c1c73c3750059ee26defef3fa6f4823b78 100644
--- a/typo3/sysext/backend/Tests/Unit/Form/FormDataProvider/SiteDatabaseEditRowTest.php
+++ b/typo3/sysext/backend/Tests/Unit/Form/FormDataProvider/SiteDatabaseEditRowTest.php
@@ -76,7 +76,7 @@ class SiteDatabaseEditRowTest extends UnitTestCase
     {
         $input = [
             'command' => 'edit',
-            'tableName' => 'sys_site',
+            'tableName' => 'site',
             'vanillaUid' => 23,
             'customData' => [
                 'siteIdentifier' => 'main',
@@ -114,7 +114,7 @@ class SiteDatabaseEditRowTest extends UnitTestCase
     {
         $input = [
             'command' => 'edit',
-            'tableName' => 'sys_site_errorhandling',
+            'tableName' => 'site_errorhandling',
             'vanillaUid' => 23,
             'inlineTopMostParentUid' => 5,
             'inlineParentFieldName' => 'invalid',
@@ -140,7 +140,7 @@ class SiteDatabaseEditRowTest extends UnitTestCase
     {
         $input = [
             'command' => 'edit',
-            'tableName' => 'sys_site_language',
+            'tableName' => 'site_language',
             'vanillaUid' => 23,
             'inlineTopMostParentUid' => 5,
             'inlineParentFieldName' => 'invalid',
@@ -166,7 +166,7 @@ class SiteDatabaseEditRowTest extends UnitTestCase
     {
         $input = [
             'command' => 'edit',
-            'tableName' => 'sys_site_language',
+            'tableName' => 'site_language',
             'vanillaUid' => 23,
             'inlineTopMostParentUid' => 5,
             'inlineParentFieldName' => 'languages',
diff --git a/typo3/sysext/core/Classes/Site/Entity/SiteLanguage.php b/typo3/sysext/core/Classes/Site/Entity/SiteLanguage.php
index f4092899afac2e675a0aeaf70eceb7432b588b31..ced7eb505cdd8b9ce479e59f8562f1c383f8d470 100644
--- a/typo3/sysext/core/Classes/Site/Entity/SiteLanguage.php
+++ b/typo3/sysext/core/Classes/Site/Entity/SiteLanguage.php
@@ -17,7 +17,7 @@ namespace TYPO3\CMS\Core\Site\Entity;
  */
 
 /**
- * Entity representing a sys_sitelanguage configuration of a site object.
+ * Entity representing a site_language configuration of a site object.
  */
 class SiteLanguage
 {
diff --git a/typo3/sysext/core/Documentation/Changelog/9.2/Feature-84581-SiteHandling.rst b/typo3/sysext/core/Documentation/Changelog/9.2/Feature-84581-SiteHandling.rst
index f1d97d799c8defcc53765ab6dae5bbfc503f86da..fd3eea64f1313904fd226d611d61113791a75610 100644
--- a/typo3/sysext/core/Documentation/Changelog/9.2/Feature-84581-SiteHandling.rst
+++ b/typo3/sysext/core/Documentation/Changelog/9.2/Feature-84581-SiteHandling.rst
@@ -139,6 +139,54 @@ Root pages are identified by one of these two properties:
 * they have the "Use as Root Page" property in `pages` set to true.
 
 
+Configuration
+=============
+
+The new backend module relies on FormEngine to render the edit interface. Since the form data is not stored in
+database records but in :file:`.yml` files, a couple of details have been extended of the default FormEngine code.
+
+The render configuration is stored in :file:`typo3/sysext/backend/Configuration/SiteConfiguration/` in a format
+syntactically identical to TCA. However, this is **not** loaded into :php:`$GLOBALS['TCA']` scope, and only a small
+subset of TCA features is supported.
+
+**Extending site configuration is experimental** and may change any time.
+
+In practice the configuration can be extended, but only with very simple fields like the basic config type :php:`input`,
+and even for this one not all features are possible, for example the :php:`eval` options are limited. The code throws
+exceptions or just ignores settings it does not support. While some of the limits may be relaxed a bit over time, many
+will be kept. The goal is to allow developers to extend the site configuration with a couple of simple things like 
+an input field for a Google API key. However it is **not possible to extend with complex TCA** like inline relations,
+database driven select fields, Flex Form handling and similar.
+
+The example below shows the experimental feature adding a field to site in an extensions file
+:file:`Configuration/SiteConfiguration/Overrides/sites.php`. Note the helper methods of class
+:php:`TYPO3\CMS\core\Utility\ExtensionManagementUtility` can not be used.
+
+.. code-block:: php
+
+    <?php
+    // Experimental example to add a new field to the site configuration
+
+    // Configure a new simple required input field to site
+    $GLOBALS['SiteConfiguration']['site']['columns']['myNewField'] = [
+        'label' => 'A new custom field',
+        'config' => [
+            'type' => 'input',
+            'eval' => 'required',
+        ],
+    ];
+    // And add it to showitem
+    $GLOBALS['SiteConfiguration']['site']['types']['0']['showitem'] = str_replace(
+        'base,',
+        'base, myNewField, ',
+        $GLOBALS['SiteConfiguration']['site']['types']['0']['showitem']
+    );
+
+The field will be shown in the edit form of the configuration module and it's value stored in the .yml
+file. Using the site object :php:`TYPO3\CMS\core\Site\Entity\Site`, the value can be fetched using
+:php:`->getConfiguration()['myNewField']`.
+
+
 Impact
 ======