I’ve been working on trying to better document the whole flow of code that goes into a build of firmware for an OpenPOWER machine. This is partially to help those not familiar with it get a better grasp of the sheer scale of what goes into that 32/64MB of flash.

https://www.flamingspork.com/blog/2017/12/11/a-simplified-view-of-openpower-firmware-development/