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!