A very belated update to this: Nick Moore, Tim, and Damien George (MicroPython creator) had a chat at PyCon AU 2018. It sounded like there was interest in merging it back upstream at some point, particularly if it acquired Device Tree support for hardware config, and thus was usable on more platforms. As part of this I've updated FuPy MicroPython to be current with upstream MicroPython 1.9.4+, and moved the litex directory to ports/fupy consistent with the rearrangement that happened upstream a while ago.

FTR, it sounded like the best approach was to keep merging in Upstream MicroPython until we had something we were fairly happy was in a working/useful to merge upstream state, and then rebase on top of the current upstream at the time and ask about merging that.

Ewen