on the command line you can modify the device tree blobs with fdtget/fdtput
to get the status of any given node:
# fdtget /boot/dtb/bcm2837-rpi-3-b.dtb /soc/spi@7e204000 status
disabled
to change the status of the node
# fdtput --type s /boot/dtb/bcm2837-rpi-3-b.dtb /soc/spi@7e204000 status okay
but i don't know if enabling the spi stuff in the dtb will make your device
accessible
my issue was i wanted to add an ethernet device to spi on fedora, and i had to actually
patch dts files and rebuild the dtb completely