I received NanoPi NEO and NEO Air boards along with the NanoHat PCM5102a that FriendlyArm is selling: http://www.friendlyarm.com/index.php?route=product/product&product_id=169
It's a good quality audio stereo out addon board compatible with NEO and NEO Air.
I got it working with Armbian on NEO Air!
I adapted commits from FA's repo to match Armbian's tree and get that DAC working, (original commits here: https://github.com/friendlyarm/h3_lichee/search?utf8=%E2%9C%93&q=pcm5102a+&type=Commits).
Add these to 'userpatches/kernel/sun8i-default`: https://gist.github.com/Simon-L/c8c119c86d7d3fe4316387c3ae818379
Add this config to 'userpatches' to have the driver built-in: https://gist.github.com/Simon-L/56bf6a3ec423e37973ee0da0bc16979f
Then run './compile.sh'
The fex file also needs to be modified, you can use this one: https://gist.github.com/Simon-L/f0c88190814f0f482773e81512e56553
This should be all that's needed!
Test it with 'aplay /usr/share/sounds/alsa/Noise.wav'
and install madplay if you want to try with mp3 files.
Can I safely share the content of the /boot folder and expect it to work for user copy-pasting it to the /boot folder on their sdcard? It has the kernel and the fex which are the only files the process has modified.
Obviously you'd still have to trust me 
I'm trying to turn this into a more straightforward way. Do I need to commit to modify defconfig and .fex file or is it supported in userpatches/ folder as well?
There is one issue reported in syslog that doesn't seem to prevent it from working, here's the relevant part of the log:
[ 1.598532] pcm5102a_probe [ 1.607823] asoc: snddaudio <-> pri_dai mapping ok [ 1.610531] ------------[ cut here ]------------ [ 1.610583] WARNING: at fs/sysfs/dir.c:508 sysfs_add_one+0x8c/0xac() [ 1.610604] sysfs: cannot create duplicate filename '/devices/platform/snddaudio' [ 1.610625] Modules linked in: [ 1.610694] [<c0016a20>] (unwind_backtrace+0x0/0xe8) from [<c0617cc0>] (dump_stack+0x20/0x24) [ 1.610742] [<c0617cc0>] (dump_stack+0x20/0x24) from [<c0029750>] (warn_slowpath_common+0x5c/0x74) [ 1.610788] [<c0029750>] (warn_slowpath_common+0x5c/0x74) from [<c00297a8>] (warn_slowpath_fmt+0x40/0x48) [ 1.610833] [<c00297a8>] (warn_slowpath_fmt+0x40/0x48) from [<c017aab8>] (sysfs_add_one+0x8c/0xac) [ 1.610877] [<c017aab8>] (sysfs_add_one+0x8c/0xac) from [<c017acb8>] (create_dir+0x70/0xc4) [ 1.610917] [<c017acb8>] (create_dir+0x70/0xc4) from [<c017b0bc>] (sysfs_create_dir+0xc4/0xe4) [ 1.610965] [<c017b0bc>] (sysfs_create_dir+0xc4/0xe4) from [<c0306bf0>] (kobject_add_internal+0xdc/0x1d0) [ 1.611013] [<c0306bf0>] (kobject_add_internal+0xdc/0x1d0) from [<c0306ef8>] (kobject_add+0x78/0x90) [ 1.611064] [<c0306ef8>] (kobject_add+0x78/0x90) from [<c03b0078>] (device_add+0xf8/0x578) [ 1.611114] [<c03b0078>] (device_add+0xf8/0x578) from [<c03b4208>] (platform_device_add+0x110/0x16c) [ 1.611161] [<c03b4208>] (platform_device_add+0x110/0x16c) from [<c03b47a4>] (platform_device_register+0x30/0x34) [ 1.611214] [<c03b47a4>] (platform_device_register+0x30/0x34) from [<c08f6f94>] (sunxi_snddaudio0_init+0x54/0xa4) [ 1.611263] [<c08f6f94>] (sunxi_snddaudio0_init+0x54/0xa4) from [<c000867c>] (do_one_initcall+0xa8/0x164) [ 1.611313] [<c000867c>] (do_one_initcall+0xa8/0x164) from [<c08d1a74>] (kernel_init+0x168/0x254) [ 1.611364] [<c08d1a74>] (kernel_init+0x168/0x254) from [<c000f1b0>] (kernel_thread_exit+0x0/0x8) [ 1.611455] ---[ end trace bd16a9742f20e8dd ]--- [ 1.611481] ------------[ cut here ]------------ [ 1.611509] WARNING: at lib/kobject.c:198 kobject_add_internal+0x180/0x1d0() [ 1.611533] kobject_add_internal failed for snddaudio with -EEXIST, don't try to register things with the same name in the same directory. [ 1.611560] Modules linked in: [ 1.611601] [<c0016a20>] (unwind_backtrace+0x0/0xe8) from [<c0617cc0>] (dump_stack+0x20/0x24) [ 1.611644] [<c0617cc0>] (dump_stack+0x20/0x24) from [<c0029750>] (warn_slowpath_common+0x5c/0x74) [ 1.611686] [<c0029750>] (warn_slowpath_common+0x5c/0x74) from [<c00297a8>] (warn_slowpath_fmt+0x40/0x48) [ 1.611732] [<c00297a8>] (warn_slowpath_fmt+0x40/0x48) from [<c0306c94>] (kobject_add_internal+0x180/0x1d0) [ 1.611778] [<c0306c94>] (kobject_add_internal+0x180/0x1d0) from [<c0306ef8>] (kobject_add+0x78/0x90) [ 1.611825] [<c0306ef8>] (kobject_add+0x78/0x90) from [<c03b0078>] (device_add+0xf8/0x578) [ 1.611870] [<c03b0078>] (device_add+0xf8/0x578) from [<c03b4208>] (platform_device_add+0x110/0x16c) [ 1.611915] [<c03b4208>] (platform_device_add+0x110/0x16c) from [<c03b47a4>] (platform_device_register+0x30/0x34) [ 1.611962] [<c03b47a4>] (platform_device_register+0x30/0x34) from [<c08f6f94>] (sunxi_snddaudio0_init+0x54/0xa4) [ 1.612007] [<c08f6f94>] (sunxi_snddaudio0_init+0x54/0xa4) from [<c000867c>] (do_one_initcall+0xa8/0x164) [ 1.612052] [<c000867c>] (do_one_initcall+0xa8/0x164) from [<c08d1a74>] (kernel_init+0x168/0x254) [ 1.612098] [<c08d1a74>] (kernel_init+0x168/0x254) from [<c000f1b0>] (kernel_thread_exit+0x0/0x8) [ 1.612125] ---[ end trace bd16a9742f20e8de ]---
Any hint? The codec still works fine. There is no control in alsamixer.
Thanks to @tkaiser and @Igor for their help on IRC.