Daniel,
[First, if you have the topology setup in true Campus style, then all of the APs are using MiNT level-1 links for adoption and management. If you are instead using MiNT level-2 adoption, then the below does not apply]
This is supported. To avoid potential network loops though - if the same broadcast domain (VLAN) is used across the several buildings for all the APs - then you need to configure the APs within each new building-RFDomain to operate under its own unique MiNT area-id value.
If all your APs are currently using the same single AP Profile (for a hardware model type), this would mean that you will now have to create copies of the AP Profile and make them specific/apply to just the APs in each building (RFDomain). (example: AP Profile ap7632-Building-1, ap7632-Building-2, etc, each being the same except having a different/unique MiNT Area ID) This way, any APs using the Profile for that building (RFDomain) will also begin using that building's new custom MiNT area ID.
To set the custom MiNT area-id for each AP Profile, in the CLI, enter:
mint level 1 area-id
commit write
In the UI,
Configuration -> Profiles -> (AP Profile) -> Advanced -> MiNT Protocol -> (Check box for Level 1 Area ID and set value)
Commit and Save
Obviously, you'll then need to go back and complete the rest of the various settings for each new RFDomain, right?