Freeradius 3.0 and realms

Is there good documentation of the changes made to realms between freeradius 2 and freeradius 3? We're trying to get windows machine login to work, and we're having the same problem as before. Once the machine is joined to the domain, Windows appends the domain to the machine name. We need to strip the domain off to find the proper identity. In freeredius 2, I was able to define a realm which did that, but that format no longer works for freeradius 3, and there seems to be no useful breadcrumb for how to create the new style realm.