Extruding the camera block for my phone model I want to do in my 3D model a bulging camera block. Of course, I know this can be done using the "extrude" tool. But I can't use subdivide modifier, consequently I can't do that. And I want to do a "notches" (It's Google Translate, not me) for power button (like power button in Moto Inc. Smartphones)



  So, I hope you understand me, because I'm not good in english. Please, don't throw tomatoes at me :) And remember, I don't want to steal someone's design of smartphone, I'm just learning to do something like this.


This is my .blend file:
Here is an edit of your object with a more detailed topology (ngons at minimum, and you can easily replace them with quads, preferably, if you need to subdivide those faces).

It is not finished and it has a n X mirror modifier, but you can see that the "camera block" is quite easy to do now, and (after applying the X mirror, maybe) also side buttons, with a regular manual subdivision with CTRLR.



Here is the .blend file. Hth.