[throwaway173738]

Does the U-boot in the SPI-NOR not support booting from NVMe? It might also be possible to patch that in from mainline if it exists. You can also often provide a “boot script” in the vfat partition that overrides the boot config in non volatile memory. This was something Freescale did with the i.MX6 that became a relatively standard thing for vendor-supplied U-boot.

[daneel_w]

The default setup does not support it for any Rockchip SoC up to and including the RK3399, which is why everyone goes for tow-boot on SPI for their Pine devices. The SoCs have a hardcoded boot sequence which includes SPI, SD, USB and eMMC, but not PCIe. It is however available since the RK3588 - e.g. the Radxa Rock5B boots from NVMe right off the bat.