this gets down to personal preferences, but i like describing what the controller does or is in charge of.
Sitepages, Contact, Userlogin. if it's something like "search" then be specific Sitesearch, Productsearch, Articlesearch, Customersearch, etc
also i would try and avoid naming things Site_controller, or User_model. The controllers are always in the controller folder so it doesn't need to say controller,
and controllers call models so you don't need the word "model" or "_m" in the model name. The models are the resources that the Controller is working with.
Those model resources can do things like apply business logic - but they are always going to return a message or data back to the controller.