Default [Q] booting the android os

hello, eh i am new at this forum but i am not new with the android
so i know how to make a rom from scratch & .....
this question is : if i have a processor & ram & .... etc how do i install the android bootoader
i know this is a hardware or an off-topic question but i just need any link that could help
(if it is based onBios how does it really works & it is possible to boot via grub ?)