In i.MX8MQ and i.MX8M Mini, the codec used is WM8524, which only supports audio playback. Although 8M Mini does have PDM microphone interface (MICFIL), there is no support for audio record via I2S. This guide will show you how to add audio recording driver in i.MX8MQ/8MM step by step.
Hardware: i.MX8MQ/8MM Evk, I2S output digital microphone
Kernel version: 4.14.78
For detailed steps, please see attachment.