Enabling SPI in OpenWrt on a Raspberry Pi

On a Raspberry Pi OS there is a rpi-config that lets me enable spi to work with it.
This is a description of what I want to do: https://pimylifeup.com/raspberry-pi-spi/

How can I do the same on openWRT?

related Using SPI on a Raspberry Pi ?

Thanks, but the opkg package kmod-spi-gpio-custom does not exist on my rpi3b+.
I found this related topic as well setting-spi-configs-rpi3b but adding to boot/config.txt the dtparam=spi=on does not export me the needed /dev/spi folders.
There may be something missing in that description...