Redirect SPDIF In to 5.1 out


I have a USB Soundcard connected to my Raspberry Pi. The Soundcard have an SPDIF In that i want to use to redirect that incomming sound to the analog outputs. I searched the internet already but didnt found a answer to my question.
Until now i use the ALSA Drivers for the soundcard.

My System:
Raspberry Pi 3 Model B
Newest OSMC with Kodi 17