add RBAC support

PROD-17451

Change-Id: Ib28b3d514de7f70ccd5faafa96d791ae64c7df24
diff --git a/README.rst b/README.rst
index d465fac..5c014a2 100644
--- a/README.rst
+++ b/README.rst
@@ -781,6 +781,20 @@
         multi_tenancy: false
       ...
 
+Enable RBAC
+-----------
+
+
+.. code-block:: yaml
+
+    opencontrail:
+      ...
+      config:
+        aaa_mode: rbac
+        cloud_admin_role: admin
+        global_read_only_role: member
+      ...
+
 Switch from on demand to periodic keystone sync
 -----------------------------------------------