added what's new.md

Author: vpattnai

defender-xdr/whats-new.md

@@ -32,6 +32,7 @@ You can also get product updates and important notifications through the [messag
 
 ## December 2024
 
+- The new [Defender Experts Scoped Coverage](defender-experts-scoped-coverage.md) feature provides customers the functionality to define a specific set of devices and/or users, based on geography, subsidiary, or function, for which they'd like Defender Experts to provide support.
 - (Preview) The [Link to incident](advanced-hunting-defender-results.md#link-query-results-to-an-incident) feature in Microsoft Defender advanced hunting now allows linking of Microsoft Sentinel query results. In both the Microsoft Defender unified experience and in [Defender XDR advanced hunting](advanced-hunting-link-to-incident.md), you can now specify whether an entity is an impacted asset or related evidence.
 - (Preview) In [advanced hunting](advanced-hunting-defender-use-custom-rules.md#use-adx-operator-for-azure-data-explorer-queries-preview), Microsoft Defender portal users can now use the `adx()` operator to query tables stored in Azure Data Explorer. You no longer need to go to log analytics in Microsoft Sentinel to use this operator if you are already in Microsoft Defender.
 -  New documentation library for Microsoft's unified security operations platform. Find centralized documentation about [Microsoft's unified SecOps platform in the Microsoft Defender portal](/unified-secops-platform/overview-unified-security). Microsoft's unified SecOps platform brings together the full capabilities of Microsoft Sentinel, Microsoft Defender XDR, Microsoft Security Exposure Management, and generative AI into the Defender portal. Learn about the features and functionality available with Microsoft's unified SecOps platform, then start to plan your deployment.