It depends on the match rules you are playing under. If it is an academy game, then it probably falls under slightly modified Laws of the Game.
You must also remember that things get lost in translation, especially when bias is involved. Was it "chanting/cheering" or something else?
ATR 5.10 addresses some of this:
5.10 BEHAVIOR OF COACH AND BENCH PERSONNEL
Coaches or other team officials, one at a time, may provide tactical advice to their players, including
positive remarks and encouragement. The referee should only take action against coaches or other
team officials for irresponsible behavior or for actions that bring the game into disrepute. A coach or
other team official may not be cautioned or sent off nor shown any card; however, at the discretion of
the referee, such persons may be warned regarding their behavior or expelled from the field of play and
its immediate area.
12.28.8 MISCONDUCT BY A SUBSTITUTE
Substitutes may be cautioned and shown the yellow card only for:
• Unsporting behavior
• Dissent
• Delaying the restart of play
The way you describe it, it may be a situation where the referee "warns" the players in the technical area. If all they were doing was cheering in a normal manner, then there's no reason to do that.
HS rules are clearly different. It's up to you to know the laws for the level of game you are officiating.
http://www.ussoccer.com/Referees/Resource-Center/Zone-1.aspx