Simple GPIO example

There is no specific binding for analog values afaik.
But what you can do is read the value of /sys/bus/iio/devices/iio:device0/in_voltage_raw and either MQTT that to openhab OR use the REST API to put it in openhab.
This is simple to do with Python.

If you dont know how, have a look at how the DS18B20 or DHTx transfers their values with a python program, it basically comes down to reading the file, parsing it to get just the one value you need and then use MQTT or REST.
REST API uses:
requests.put('http://192.168.xxx.yyy:8080/rest/items/<YOUR ITEM>/state',value) .

Maybe this tutorial can help you on your way Reading a DHT11/22 with 'overlay' and send result via REST API