Um, you have the burden backwards; closedness means a lack of documentation.

If you want to try, go here:

  https://www.nxp.com/products/processors-and-microcontrollers/arm-processors/i-mx-applications-processors/i-mx-8-processors/i-mx-8m-family-armcortex-a53-cortex-m4-audio-voice-video:i.MX8M?tab=Documentation_Tab

And try to download the "Security Reference Manual for i.MX 8M Dual/8M QuadLite/8M Quad". You can't. It's only available under NDA to extremely high-volume customers. And that manual is where all the goodies are.