How many mound visits can a team make?

• Teams are limited to four mound visits per nine innings. A team gets one extra visit for the ninth inning if it has none left at the end of the eighth, and one more for every extra inning played.
• The coaching staff (including the manager) may make one visit per pitcher per inning without removing him. If the same pitcher is visited twice in one inning, he must be removed from the game.
• Visits by managers and coaches are limited to 30 seconds, starting when the manager or coach has left the dugout and been granted time by the umpire. A visit ends when he leaves the 18-foot circle around the pitching rubber.
• Any manager, coach or player visit to the mound counts, except visits to clean cleats in rainy weather, to check a possible injury, or after an offensive substitution is announced. Normal talk between a player and the pitcher that does not need either to leave position is not a visit.
• If a team is out of visits, the umpire has discretion to allow a brief visit at the catcher's request after a cross-up between pitcher and catcher.

Source: MLB, Mound Visit (mlb.com/glossary/rules/mound-visit).