Firstly you need to educate yourself as to what porn is nowadays. Take a look at the fractured society between girls and boys at schools and how porn, smart phones etc has fuelled the toxic sexual culture that is hurting boys and girls, and their relationships between each other.
It is not good enough to hope your child will get through it ok, working out how to be a good human all by themselves.
IMO you need to have full honest discussions about sex, consent, relationships and porn addiction.
My DSS was caught with some porn that if he practised in real life would have been illegal (and I’m not just talking about age of consent). He was only 14. He had also been sending pictures of himself to others. Ok no girls were involved (let us not forget not all boys and girls are heterosexual) but he was completely being taken advantage of. My DH was forced to take his head out of the sand and parent him because his “oh we all watched it when we were young,” bullshit showed him how out of time he was.
In the end DSS’s parents got their act together and sorted it out. No phones in his room at night etc. Limits on what to look at etc.
Our youngest are going to have to sit through some very choice selection of videos to educate them on the dangers of porn, sexting, relationships etc before they even get hold of a smartphone. I have to be confident they understand the risks and understand boundaries. They have to appreciate if I catch wind of them bullying, or coercing others to do sexually inappropriate things for an under 16 they will be handed a non-smartphone.
I might be the world’s worst mother but it will be banned in my home. I do know they may see it elsewhere and that’s fine. But I will not casually accept my son or daughters watching extreme pornography in my home when there are other children in the house.
If they think I am too strict they can go chat to their big brother about it and blame him for the way we’ve become.