Request permission to allow push notification

I'm new to the android platform, and app development for it in general. On iOS, every app must ask for and confirm push notifications as required by apple, not necessarily the app. I have not noticed any apps that I've downloaded on my new Samsung phone prompting me if I want to receive push notifications, it just automatically registers me for them. Is this normal Android convention, to automatically register users for push notifications and they can disable them later? I am developing an Android application myself right now and i'm wondering.... Should I be prompting users and asking if they want them before I register them? Obviously it would be the polite thing to do to ask users permission before signing them up for push notifications. However, if that's not common practice I see no reason to potentially lose some receivers of them. Any insights / documentation to best practices for Android would be awesome.

Thanks