If you go afk during a game for several minutes, what's the punishment?

In the last 2 days I've had many games (5 or even more) during which one of my teammates went afk, dc'd or ragequitted altogether.

I'm pretty tired of having to deal with this kind of players, so I wanted to know if they will eventually receive some form of punishment. Right now it seems like everyone is able to abandon games every once in a while and walk away scot-free, so it feels like their behaviour is being legitimized.