Mircea Caprioru shares his experience with Bootlin's Embedded Linux Kernel and Driver Development course: https://shadowcoding.com/bootlin-training-experience/
Mircea was our guest community participant. We regularly invite deserving community members to join our course (see https://frama.link/_7gDd78e).
By the way, Mircea also has interesting blog posts about using a custom Linux system and U-Boot on Raspberry Pi. See on his blog: https://shadowcoding.com