Ionic custom push notifications android/iphone

I want to have push notifications in both iphone and android app. I searched and most posts are about the ionic service and plugin. I have my own server that handles push notification to devices. What I need is a way to register for push notification, send the reg id to my server, and listen to incoming push notifications on device - but not using the ionic push platform.

Can this be done? I found some cordova push articles - but do those fit ionic?