I'm experimenting to see how much of an effort it will take to get nuttx running on a nucleo-h7s3l8 board which uses a small internal flash and external octo-flash. Boot process requires a bootloader in internal flash to configure power/clocking/octo-flash and then execute the full nuttx/application from octo-flash that completes the rest of the initialization.
There are several boards in the source tree that boot in a similar two-step way. For example, all run-from-SDRAM configurations require some startup logic that initializes the SDRAM before you can run from it. The (SAM5D has several such tiny loaders. I recall it loads from SPI FLASH into IRAM where the SDRAM is initialized).
