Have you already thought about whether your friend might also be distracted unconsciously - meaning it's become a habit without him deliberately aiming it at you? That makes a difference when you want to bring it up.
Honestly, I don't think you're overreacting. If you're meeting regularly to spend time together and he's constantly looking at his screen, that's actually pretty rude. It signals "this isn't important enough to me right now". But instead of starting a confrontation right at the table, you can also handle it more casually - maybe just say in a good moment: "Hey, I've noticed you check your phone a lot when we're together. Is everything okay with you or is something bothering you?" That sounds less accusatory and also gives him a chance to explain in case something's going on in the background.
If he reacts defensively or doesn't change the behavior, you can also just set your own boundaries - be more conscious about sharing less, keep things brief, maybe shorten the meetup. He'll eventually notice that the quality of time together is suffering. Sometimes you don't need big words at all, just that the other person feels what it's like.