With the upstream device tree, the sound card is not detected at all, so ther also is no audio output.
I have never really tried to actually read the output of a decompiled binary device tree or of the /proc/device-tree folder. It sounds pretty difficult to do, given that it will not use any alias names… However, looking at my working setup (dtc -I fs /proc/device-tree), I see the devices in question (rtc, audio codec) hooked up to i2c@1c000, which I assume is what uses the i2c3 alias in the dts file.
Regarding the microphone: I too never managed to get audio-in working, but since I am not on the official Debian image, I “just” blamed my ALSA configuration. Furthermore, I figured out that what I really wanted, namely the line-in port, is not wired up to any external connector, so I would have to solder a plug to the mainboard to get it working… So, I just gave up on this and bought a USB sound card.