document genie slave config via device variable (#3096)

* document genie slave config via device variable

* Move content around

source/_components/media_player.directv.markdown

@@ -22,10 +22,55 @@ The `directv` media player platform can also be forced to load by adding the fol
 media_player:
   - platform: directv
 ```
-
 Configuration variables:
 
 - **host** (*Optional*): Use only if you don't want to scan for devices.
 - **port** (*Optional*): The port your receiver is using. Defaults to `8080`.
 - **name** (*Optional*): Use to give a specific name to the device.
+- **device** (*Optional*): Use to specify a particular receiver in a Genie setup.
 
+In a DirecTV setup with Genie slave boxes, only the master Genie server is currently found via the [discovery component](/components/discovery/). Slave boxes must be manually configured via the `device` configuration variable in order to be used with Home Assistant.
+
+To find valid device IDs, open `http://<IP Address of Genie Server>:8080/info/getLocations` in a web browser. For each Genie slave, you will find a variable `clientAddr` in the response, and this should be used for `device` in `configuration.yaml`
+
+For example, a response such as:
+
+```json
+{
+  "locations": [
+    {
+      "clientAddr": "0",
+      "locationName": "MASTER GENIE SERVER",
+      "tunerBond": true
+    },
+    {
+      "clientAddr": "5009591D6969",
+      "locationName": "SOME SLAVE GENIE"
+    }
+  ],
+  "status": {
+    "code": 200,
+    "commandResult": 0,
+    "msg": "OK.",
+    "query": "/info/getLocations"
+  }
+}
+```
+
+Could be formatted into `configuration.yaml` like so:
+
+```yaml
+media_player:
+  - platform: directv
+    host: 192.168.1.10
+    port: 8080
+    name: Main DirecTV Box
+    device: 0
+  - platform: directv
+    host: 192.168.1.10
+    port: 8080
+    name: Bedroom DirecTV
+    device: 5009591D6969
+```
+
+It is important to notice that the host and port variables for slave receivers are the same as the master receiver.