(this is a light derail but related) some of this design IS firmware - the lowest level bootstrap is encoded into an internal ROM - currently it's a very dumb

(this is a light derail but related) some of this design IS firmware - the lowest level bootstrap is encoded into an internal ROM - currently it's a very dumb bootstrap, a real implementation would boot from a number of possible sources. The sources are there on github. All the ARM systems you can buy today have a similar embedded boot loader - almost all of them do not release that source, because it's the root of their secure boot chain. IMHO this code should be public (but not the keys)