From what I have seen there isn't any. I do believe that there are punishments for too many red cards but I know of some players that have already received several yellows this year and nothing has happened to them.
I was always under the assumption that as a defender if you didn't receive a yellow card a game, you weren't playing hard enough defense. At least thats the way I played. I think it only matters in tournys how many cards you get.
