How to integrate call/Incoming/call with WearOS?

Question

We have a call(VoIP) capability in our phone app and wanted to integrate in our Wear/Watch App. We see from other apps like WhatsApp, etc the call channel is given to the Native Incoming/OutGoing call handle in the watch. We would like to know how do we integrate call channel with Wear app. We could not find much of information in Wear Documentation.