nik-ii

@sgjava the mainline device tree doesn't have the spi nodes the 3.14 had:  https://github.com/hardkernel/linux/blob/odroidc2-3.14.y/arch/arm64/boot/dts/meson64_odroidc2.dts#L802
 
That looks like generic GPIO SPI, and I haven't found, in the last 20 minutes or so, where the spicc and spifc pops out of the processor GPIO wise.  It does not appear to be GPIOX, so I think on the C2 the setup has to be a software SPI.  NanoPi K2 appears to be in the same position, just plain not having SPI.  I will investigate adding it to K2, then someone with a C2 can try it.

@nik-ii OK, I had some time to play around with my C2 which already had Armbian Stretch installed:
 
Linux hostname 4.18.8-odroidc2 #264 SMP PREEMPT Wed Sep 19 12:35:18 CEST 2018 aarch64 GNU/Linux
 
armbian-config has no Hardware menu, but it looks like GPIO and I2C are already enabled:
 
ls /dev/gpio* /dev/i2c* /dev/spi*
ls: cannot access '/dev/spi*': No such file or directory
/dev/gpiochip0  /dev/gpiochip1  /dev/i2c-0  /dev/i2c-1
 
If you go to the Odroid C2 wiki you can follow the steps to enable SPI:
 
sudo su -
 
modprobe spidev
modprobe spi_gpio
modprobe: FATAL: Module spi_gpio not found in directory /lib/modules/4.18.8-odroidc2
modprobe spi_bitbang
 
lsmod | grep spi
spi_bitbang            16384  0
spidev                 20480  0
 
ls /dev/spi*
ls: cannot access '/dev/spi*': No such file or directory
 
I'm not sure what's going on here because this works with the HardKernel OS images. I'm actually using my C2 as a Jenkins CI server, but I did play around and made sure gpio, i2c and spi worked. I believe that was a 3.x kernel though @Igor may be able to point you in a better direction to get SPI cranking.
 
There are other drivers, but I'm not sure which one to use:
 
ls /lib/modules/4.18.8-odroidc2/kernel/drivers/spi
spi-bitbang.ko    spi-butterfly.ko  spidev.ko  spi-lm70llp.ko  spi-meson-spifc.ko
 
 

@nik-ii I actually have a C2 and I think I just loaded mainline on it a few weeks ago.  I'll check tonight, but if your SBC is using mainline then it should work.  With armbian-config you need to enable SPI, I2C, etc. I'll reply back here later with C2 specific info.
 
Note from your pic that GPIO is showing up.