You can definitely mount a TV over a fireplace. This is a popular idea. Some folks recommend against this, partly because it puts the TV at an awkward angle and partly because the heat and soot from the fireplace may interfere with the lifespan of the TV. If you’re really set on this option though, it’s doable.
Mounting the TV to a brick fireplace works just like mounting it to a wall stud. Just make sure you use a drill bit that can handle brick! You’ll also need a plan for cord storage—something to route them around the fireplace and down to the outlet.