U-Boot with direct NVMe boot support for eMMC/SPI Flash

[nyxxenator]

I might be mixing up my terminology because I'm not super experienced with the SBC stuff, but is it possible to do something like GRUB in U-Boot but where you can select a boot device? Kinda like on x86 systems where you can usually press a keyboard button while it's booting and then you get the choice of harddrive, cd drive, network or usb? Just an example. I have an old netbook where I would do that if I wanted to boot an SD card instead of the internal SSD.