add schema mapping feature

Author: austinmccollum

articles/sentinel/whats-new.md

@@ -20,12 +20,26 @@ The listed features were released in the last three months. For information abou
 
 ## September 2024
 
-
+- [Schema mapping added to the SIEM migration experience](#schema-mapping-added-to-the-siem-migration-experience)
 - [Azure reservations now have pre-purchase plans available for Microsoft Sentinel](#pre-purchase-plans-now-available-for-microsoft-sentinel)
 - [Import/export of automation rules now generally available (GA)](#importexport-of-automation-rules-now-generally-available-ga)
 - [Google Cloud Platform data connectors are now generally available (GA)](#google-cloud-platform-data-connectors-are-now-generally-available-ga)
 - [Microsoft Sentinel now generally available (GA) in Azure Israel Central](#microsoft-sentinel-now-generally-available-ga-in-azure-israel-central)
 
+### Schema mapping added to the SIEM migration experience
+
+Since the SIEM migration experience became generally available in May 2024, steady improvements have been made to help migrate your security monitoring from Splunk. The following new features let customers provide more contextual details about their Splunk environment and usage to the Microsoft Sentinel SIEM Migration translation engine:
+
+- Schema Mapping
+- Support for Splunk Macros in translation
+- Support for Splunk Lookups in translation
+
+To learn more about these updates, see [SIEM migration experience](siem-migration.md).
+
+For more information about the SIEM migration experience, see the following articles:
+- [Become a Microsoft Sentinel ninja - migration section](https://techcommunity.microsoft.com/t5/microsoft-sentinel-blog/become-a-microsoft-sentinel-ninja-the-complete-level-400/ba-p/1246310#toc-hId-111398316)
+- [SIEM migration update - Microsoft Sentinel blog](https://techcommunity.microsoft.com/t5/microsoft-sentinel-blog/siem-migration-update-now-migrate-with-contextual-depth-in/ba-p/4241234)
+
 ### Pre-purchase plans now available for Microsoft Sentinel
 
 Pre-purchase plans are a type of Azure reservation. When you buy a pre-purchase plan, you get commit units (CUs) at discounted tiers for a specific product. Microsoft Sentinel commit units (SCUs) apply towards eligible costs in your workspace. When you have predictable costs, choosing the right pre-purchase plan saves you money!