doc: update ChangeLog

Signed-off-by: Joachim Wiberg <troglobit@gmail.com>

Author: troglobit

doc/ChangeLog.md

@@ -9,6 +9,9 @@ All notable changes to the project are documented in this file.
 ### Changes
 
 - Upgrade Linux kernel to 6.18.23 (LTS)
+- Add support for PTP/gPTP (IEEE 1588-2019 / 802.1AS) clock synchronization.
+  Supported clock types: Ordinary Clock, Boundary Clock, and Transparent Clock.
+  See the User Guide for configuration details
 - Add support for [Banana Pi BPI-R4][BPI-R4], quad-core Cortex-A73 router with
   4x 2.5 GbE switching, dual 10 GbE SFP+.  Variants BPI-R4-2g5 and BPI-R4P have
   one SFP+ replaced by a 2.5 GbE RJ45, with optional PoE on the R4P