doc: release-notes-3.7: Add MDIO release notes

Add release notes for MDIO drivers.

Signed-off-by: Declan Snyder <declan.snyder@nxp.com>
diff --git a/doc/releases/release-notes-3.7.rst b/doc/releases/release-notes-3.7.rst
index 520c131..235e07d 100644
--- a/doc/releases/release-notes-3.7.rst
+++ b/doc/releases/release-notes-3.7.rst
@@ -841,6 +841,11 @@
 
 * MDIO
 
+  * Made the bus_enable and bus_disable functions optional for drivers to implement,
+    and removed empty implementation from many drivers.
+  * Added NXP ENET QOS MDIO controller driver.
+  * Fixed but with NXP ENET MDIO driver blocking the system workqueue.
+  * :kconfig:option:`CONFIG_MDIO_NXP_ENET_TIMEOUT` units change to microseconds.
   * Added support for STM32 MDIO controller driver.
 
 * MFD