Finding documentation and other resources for N9 (and N950) development is not hard, but it's a bit too spread around. Generic Qt information can be found on the Nokia Qt site, then N9 specific stuff are in another place. Then there are at least 3 forums to follow.
I started writing this some time ago already, I was going to write some more later when I had time but this post is more or less what I was about to write. So there, go read it.