[coreboot] Recommended workflow with Chromebook support

Folks,
This question is directed at the Coreboot developers who target a 
Chromebook device.

Do you tend to do bulk of development and testing within chromiumos 
coreboot tree or directly in coreboot.org tree?

As we get going we are trying to decide if it makes more sense to work 
directly in chromium tree and then rebase our commits onto coreboot tree 
and test compile prior to submission upstream?
Cheers,
T.mike