Cross-AZ high availability for L3 routers

Closes-Bug: PROD-34390

Change-Id: I6410fb7de9d363c376439a26600810cf6453291c
diff --git a/README.rst b/README.rst
index ef03f8b..7de9c8f 100644
--- a/README.rst
+++ b/README.rst
@@ -1761,6 +1761,41 @@
         availability_zone: nova
       ....
 
+High-available cross-az L3 routers:
+-----------------------------------
+
+Control node:
+
+.. code-block:: yaml
+
+    neutron:
+      ....
+      server:
+        router_scheduler_driver: neutron.scheduler.l3_agent_scheduler.AZLeastRoutersScheduler
+        max_l3_agents_per_router: '3'
+      ....
+
+Network/Gateway node:
+
+.. code-block:: yaml
+
+    neutron:
+      ....
+      gateway:
+        availability_zone: nova
+      ....
+
+Compute node:
+
+.. code-block:: yaml
+
+    neutron:
+      ....
+      compute:
+        availability_zone: nova
+      ....
+
+
 Set nova_metadata_protocol for Neutron
 ---------------------------------------