[DOCS] - OpenHAB integration complement (#1833)

docs/integrate/openhab3.md

@@ -1,7 +1,7 @@
-# Integrate OPENHAB3
+# Integrate OPENHAB 3/4
 
-This tutorial will show how to integrate the BLE gateway to OpenHAB3 leveraging the auto discovery functionality.
-After this tutorial, you should see your Bluetooth Low Energy devices in OpenHAB3 without any file based manual configuration.
+This tutorial will show how to integrate the BLE gateway to OpenHAB 3 or 4 leveraging the auto discovery functionality.
+After this tutorial, you should see your Bluetooth Low Energy devices in OpenHAB without any file based manual configuration.
 
 ## Prerequisites
 * OpenHAB 3.3 or higher
@@ -80,6 +80,9 @@ To make the auto discovery compatible with OpenHAB you have to send the followin
 
 `mosquitto_pub -t "home/OpenMQTTGateway/commands/MQTTtoSYS/config" -m '{"ohdisc":true}'`
 
+You can also activate OpenHAB auto discovery by adding the gateway as a Thing, Model, and switching the button to ON. The name of the channel to add is "SYS: OpenHAB discovery".
+Once activated restart OpenMQTTGateway.
+
 ## Adding the things
 1. From the Administration click on "Things" under "Settings", you should see a number in the INBOX button