Law 12 makes it clear that ANY player commits an offence if that player plays the ball whilst it is on the floor. So, is an offence committed in the following circumstances:
A: the gk has to make a save by going to the floor. So, when he/she comes into contact with the ball the gk is on the ground.
B: a gk makes a first save, which remains in play. However, the gk, while still on the ground, makes a second save following an opponent's attempt to score from the keeper's initial save.
C: a gk completes a save by going to the floor. However, instead of standing up to release the ball back into play, the gk releases the ball to a player on his/her own side WHILST REMAINING ON THE FLOOR