isogashii/fernly ? reverse-engineered prompt

Build me a small research OS for the Fernvale board that I can use to poke around the hardware and test how the chip works.

I want it to boot on the device, give me a simple command line over serial, and let me run commands to read and write memory, control the LEDs, talk to the LCD, keypad, SPI, sleep and reboot the board, and inspect interrupts. It should also have the special flashrom mode so I can connect to flashrom and back up or restore the onboard flash.

Please make it easy to build for ARM with make, and include the bootloader pieces needed to load the firmware over USB from a Linux machine. If anything about the board behavior or tool setup is unclear, look up the current docs online and make sensible choices. Keep it simple and focused on hardware exploration, not a full operating system.