Services IoT Device Discovery

I am looking to find services offered by one of my IoT / Gateway devices. The Gateway device supports mDNS, so I can detect the local device with mDNS discovery, at this point I can see my gateway IP and listen to it.

Now I want to query what are all the services offered by the same device, how can I do this. (Assuming the gateway has a http REST service)

Is there any semantic query for IoT devices? or any other to request the services offered by the device?

Any direction or guidance, thanks in advance

~ Ashok