Add ability to specify additional physnets

Along with default external, tenant and ironic nets there
should be an ability to specify other physical networks
which customers may want to use in an openstack cluster.

Change-Id: I648d5095c534a58385da1880b18fe989684adcd0
Related-Prod: PROD-20255
diff --git a/README.rst b/README.rst
index 3e01825..9cbd45a 100644
--- a/README.rst
+++ b/README.rst
@@ -674,6 +674,33 @@
             ovs:
               driver: openvswitch
 
+Neutron with additional physical networks
+-----------------------------------------
+
+Neutron Server only
+
+.. code-block:: yaml
+
+    neutron:
+      server:
+        version: ocata
+        ...
+        backend:
+          engine: ml2
+          tenant_network_types: "flat,vlan" # Can be mixed flat,vlan,vxlan
+          ...
+          # also need to configure corresponding additional bridge_mappings on
+          # compute and gateway nodes
+          physnets:
+            sriov_net:
+              mtu: 9000 # Optional, defaults to 1500
+              vlan_range: '100:200' # Optional
+            ext_net2:
+              mtu: 1500
+          mechanism:
+            ovs:
+              driver: openvswitch
+
 Advanced Neutron Features (DPDK, SR-IOV)
 ----------------------------------------