How do I Build an Android rom for New Device?

I want to learn how to build a rom for an new device that no one has created a custom rom for. I am kinda new at this. But I want to learn how. I is there a full on guild or something on how to do it... I want to know. There are devices out there that have to custom roms yet that I would like to build for. I would like to use AOSP to build a clean fresh pure Android rom. Those devices I want to build for have the right specs to run a newer Android version but the developers did not realse an update for. I really would like to learn how to build/create my own Android rom from scratch... Learn how to build a kernel, bootloader, etc. to help the rom run right. Can anyone help?