@Londonhouse32 is the issue him waking everyone else or the TV specifically?
If it's waking everyone else that's fair - my son is almost 6 and and has always been an early riser, anything after 4.30 sometimes although recently it's more around 6am most days, which feels more normal!
He usually calls for me or comes into our room, I'll go down with him and remind him to be quiet for a bit as lots of people will still be asleep. We put the telly on and have breakfast etc then we'll play a bit before we start getting ready to go out (if not a school day)
The thing is, even if he WOULD stay in his room and play or whatever (he absolutely couldn't), that would probably be more disruptive than a bit of telly (if it's at a sensible volume) because he'd be tipping Lego/Playmobil out, rummaging through it, talking to himself acting bits out etc. His room is next to ours so we'd be awake listening to it all anyway.
But I'd absolutely be telling him he needs to keep the noise down and messing with lights and stuff, especially if it's waking siblings.
And I'd think about cutting YouTube out of he's going downstairs on his own. My friend has set up an old telly and dvd player in her son's room, he wakes early and puts a dvd - everyone is still in bed and she knows he's watching something that's fine/not rolling onto anything unsuitable or online etc.