I saw the incident on Sunday, it was live on Supertennis channel. I didn't watch the whole match beacuse I had to go out but watched up to early in the 2nd set.
I did record the match so can check it again when I get home but if I remember Djokovic hit a serve that was called out which Tsonga returned into the net (backhand side) but was overuled after a challenge. I must admit I was expecting a 1st serve to be called and so did Djokovic because I'm sure he got two balls to serve again but the Umpire gave the point to Djokovic which is when Tsonga protested. He didn't overdo it with the Umpire just made his point very stridently.
You could argue the Umpire was in his rights to award the point to Djokovic but it appreared to me both parties were expecting a first serve / replay the point.
I will have to watch it again to see if I recall events correctly.