No, it is just the only really device specific code that is able to start an OS if it provides a valid bootflow. In x86 terminology, this is the BIOS.
With this in place you are able to place an OS image (fedora, DietPi, Armbian, …) alongside, be it via NVME, USB, microSD or eMMC, and it is able to start it.
If you want to colocate it in the OS image, you have to ensure the partition layout of the OS spares the firmware area.
This is not the case with fedora, for example. If the firmware is e.g. in the eMMC, the OS image should reside in NVME, USB or microSD.
That’s why I prefer devices with SPI NOR Flash for firmware, but it is not really a showstopper.
Ok, have had an extremely busy past month but finally have some time to try this.
to dd your firmware onto a storage device do I need to partition it first? so if I will attept with SD card, dd to /dev/sda or /dev/sda1 after partitioning?
And then if I have a .img file for an OS installer, does that belong in the same partition as your firmware? Or are you saying it goes on a completely different device, e.g. your firmware on SD card, OS on eMMC? (afaik there’s no SPI NOR flash chip on this device)
Partition layouts are datastuctures obeyed by OS, MASK ROM code has no knowledge
about it. It does only absolut device addressing. Hence the “entire device to
be used” (e.g. /dev/sda).