https://www.shielder.com/blog/2022/03/reversing-embedded-device-bootloader-u-boot-p.1/
https://www.shielder.com/blog/2022/03/reversing-embedded-device-bootloader-u-boot-p.2/
https://blog.attify.com/bootloaders-part1/
https://blog.attify.com/to-boot-or-not-to-boot-das-u-boot/
https://blog.attify.com/to-boot-or-not-to-boot-practical-attack-vector/