Fuck it I'll bite.

I'm now a college student that spent my pubescent years watching porn and jerking off. My parents never really brought up sex or porn directly, they would only mention that they didn't approve of porn because it made you expect something fake.

Let me tell you one thing, it will start vanilla and maybe not often, but if constant access is available, eventually something crazy will come up(bdsm, watersports, trannys) and more than likely hell find something that is exciting to him. I personally liked japaneeze doujin's growing up (Hentai).

If it gets to this point, for the love of god don't over react. Just because he's into something strange doesn't mean he's been corrupt. I turned out fine and lead a normal life/sexual life.

My point here really is this. Don't actively deny him what he's after. But don't allow it. Create a system where he thinks he's going under the radar, it will more than likely lower the frequency he attempts to jerk it.

If you completely bar it, trust me he will find a way.

And as well, make sure you talk to him about it. Give him a fair explanation of things and please don't demonize it. Let him know what's happening to his body and that it's normal.

If he's a reader there are a few books out there that explain puberty better than most adults can. Buy one and give it to him. Trust me, it will help.

TLDR: this isn't a huge deal. Talk to him about his body and sex. Make sure he understands. Set restrictions, don't completely block it.