How do you write U-Boot to SPI NOR flash?
Without a working driver upstream, the best I can think of now is just using the shipped U-Boot/Linux (Petitboot from the manufactor). If you want to make it from source, use the shipped cross-compiler on 64 bit PC, perhaps on an archived OS, or rewrite Makefiles.
But that leaves the (for some tiny) 16 MB just for the bootloader, which doesn't even knows it's own bootdev. It seems the beforehand bootloader-loader doesn't look after SATA HDD, only SPI NOR or MMC SD. After all, just press a button to alternately load from removable card if one installed and failed to run from NOR.
Did I miss a thing in device-tree? The regulator.patch is upstream, which keeps the drives spun-up while boot (at least MMC is powered).
Thanks, yours duing.