Comment 34 for bug 1498129

Raymond: thank you for your time and effort!

Following your advice I was able to configure iec958:CARD=U7 and point it at the correct hardware device.
The following aplay command goes to the digital output:

$ aplay -D iec958:CARD=U7 test.wav

However, the pulseaudio still redirects both, Analog and Digital (S/PDIF) outputs to the same analog output.
There are no special characters in the card name.
Here is an excerpt from /usr/share/alsa/cards/USB-Audio.conf:

USB-Audio.pcm.iec958_device {
        "Xonar U7" 1
...
}

The outputs of pactl list and aplay -L are attached.
So, what shall I do with pulseaudio to recognize the iec958 output?