How to properly nest controllers?

I hwas just curious what kind of "convention" everyone uses when nesting controllers. Every time I put controllers under a folder I have them extend a controller with the same name. Is this a good practice? For example, I have an admin folder and all of the controllers under that folder extend the AdminController instead of the ApplicationController. I feel like maybe this is a little sloppy? I just need a little direction or some suggestions as to the proper way to nest controllers. Thanks!