Andre Baron

Just to summarize:
 
1. Use dtc to de-compile the existing rockchip-spi-spidev.dtbo to .dts:
    dtc -I dtb -O dts /boot/dtb/rockchip/overlay/rockchip-spi-spidev.dtbo -o rockchip-spi-spidev.dts
2. Edit the resulting rockchip-spi-spidev.dts and change instances of ff1c to ff19, and 3399 to 3328
3. (optional?) remove references to spi1, spi2, spi3
4. Compile rockchip-spi-spidev.dts back to dtbo
    dtc -I dts -O dtb rockchip-spi-spidev.dts -o /boot/dtb/rockchip/overlay/rockchip-spi-spidev.dtbo
5. Extract rockchip-fixup.script from /boot/dtb/rockchip/overlay/rockchip-fixup.scr
    (just use a text editor, and delete everything before "# overlays fixup script")
6. Edit rockchip-fixup.script and change instances of ff1c to ff19
7. Recompose rockchip-fixup.scr
   mkimage -A arm -T script -C none -d rockchip-fixup.script /boot/dtb/rockchip/overlay/rockchip-fixup.scr
 
Now, you can use armbian-config to add spidev, and reboot.