Added instructions to load Trellis apps from external repo

Also added device configuration for Stratum devices

Change-Id: Idcccb531ff3d45d7285085c6212fd5234479dc9c
diff --git a/configuration/device-config.rst b/configuration/device-config.rst
index 9a55895..1b635b8 100644
--- a/configuration/device-config.rst
+++ b/configuration/device-config.rst
@@ -63,6 +63,40 @@
       ``driver`` entirely as the correct driver configuration will be set
       automatically by ONOS
 
+
+Additional Device Configuration for Stratum Switches
+====================================================
+
+When using Stratum switches, following **additional** configurations need
+to be added to the ``basic`` section of device config.
+
+.. code-block:: json
+
+    {
+      "devices" : {
+        "device:montara1" : {
+          "segmentrouting" : {
+            "...": "...",
+          },
+          "basic" : {
+            "...": "...",
+            "managementAddress": "grpc://192.168.0.1:9339?device_id=1",
+            "driver": "stratum-tofino",
+            "pipeconf": "org.opencord.fabric.tofino.montara_sde_9_0_0"
+          }
+        }
+      }
+    }
+
+- ``managementAddress``: gRPC endpoint of the Stratum device and a numerical device ID.
+  The IP address can be replaced by domain name as well.
+
+- ``driver``: ``stratum-bmv2`` or ``stratum-tofino``, depending on which switch this is.
+
+- ``pipeconf``: A list of available pipeconfs can be dumped by running ``pipeconfs`` in ONOS CLI.
+  Select the pipeconf you would like to use for this device.
+
+
 .. caution::
     We should avoid using reserved MPLS labels for ``ipv4NodeSid`` and
     ``ipv6NodeSid``.  Please check here for the reserved values: