Documentation: Add ucm URL

This commit adds the main alsa-ucm-conf documentation
URL to PinePhone.conf, and clarifies the relevance of
the other three URLs.

Closes: #366
Signed-off-by: Boud Roukema <[email protected]>
Signed-off-by: Jaroslav Kysela <[email protected]>

ucm2/Allwinner/A64/PinePhone/PinePhone.conf

@@ -1,9 +1,16 @@
 Syntax 2
 
-# https://wiki.pine64.org/index.php/PinePhone
+# To understand (or propose bug reports) for the different
+# parts of these configuration files, see:
+# https://www.alsa-project.org/alsa-doc/alsa-lib/group__ucm__conf.html
+
+# PinePhone-specific audio card structure help:
 # https://files.pine64.org/doc/PinePhone/PinePhone%20v1.2%20Released%20Schematic.pdf
 # https://xnux.eu/devices/feature/audio-pp.html
 
+# General PinePhone help:
+# https://wiki.pine64.org/index.php/PinePhone
+
 SectionUseCase."HiFi" {
 	File "/Allwinner/A64/PinePhone/HiFi.conf"
 	Comment "Play HiFi quality music"