How graphics is handled in an embedded linux os.

Dear All,

My query is, in an embedded linux os, how graphics is handled?

To my knowledge,
Bottom-most layer must be hardware.
What is above it? Device driver from hardware vendor?
Then, on top of it, is there a hardware abstraction layer? To provide drawpixel,
drawline, draw circle etc to upperlayer?
Then, I think, other applications/windowmanagers shall be there...

This is just my idea. Got from general OS principle books.
Am I wrong?

Please help, how generally graphics are handled in an embedded linux os.
From where, we shall expect drawpixel, drawline, drawcircle etc functions?

Sincerely,
Srinivas Nayak