I'm waiting for Ludo to comment about the dots in the variable names.
(Apparently, to be forward-compatible with literal pairs, dots in variable names are not nice to use)

It would be nice to also have some clients of that stuff in that file.

I.e. actually boot the raspberry pi using some chainloader config.

Otherwise it's hard to say whether this is a good API.  When the API is actually
used it's much easier to say.