I don't recall seeing a reference to this already, nor a resolution to the open question of how to enable U-Boot for different EOMA68 configurations, so I figured it may be useful to someone to review the applicability of a talk given at the recent FOSDEM:
https://fosdem.org/2019/schedule/event/porting_u_boot_to_a_modular_device/
I hope this is helpful to someone!
Happy Hacking