It is possible to compile buildroot however it appears that overlays aren't working ...
Anyone got pointers on using overlays with buildroot and the Pi3/zero W ?
Discuss hearing, acoustics, audio injector products, - https://lists.audioinjector.net/mailman/listinfo/people
Sound card for the Raspberry Pi with inbuilt microphone : www.audioinjector.net
Audio Inector Octo multitrack GPIO sound card