I created a new mainboard based on "Bayley Bay FSP-based CRB"

It seems that (at least) the following files are mandatory for build:

cmos.layout

devicetree.cb

romstage.c

Am I right ? 

If yes - what info required to write those files ?

Can I use coreboot default files instead ?

Honestly - I thought that FSP binary configuration is all I have to do. 

And few changes in menuconfig (e.g ROM size). 

Thank you,

Zvika