MTU Mix

Good moring,

I have a question does the MTU size works by port or by unit (all the switch), the question goes because looking on different post on internet some say the MTU is by unit and other by port, so if i put on a Switch let say Powerconnect N4064 on port 1/0/1 the MTU on 9216 and on the Port 1/0/2 MTU 1536, both would work at their MTU size ?

Is there any document i can look ?