There are different linux available for different boards- called linux portsFor example a (uc)linux port for STM32F4291 Discovery kit, a linux port for Beagleboard and so on. I want to know what are the major differences and similarities between these ports?I am asking this because say, I want to take port-A for Board 1, and modify it to run on board 2.  Once I know the differences/similarities I will have a better idea of this modification required.   
Modifying linux for different boards
linux