[U-Boot] U-Boot Device Driver Development Guide

Dear Sir,

I am considering using U-Boot as a software platform to bring up a hardware platform that am developing. In doing so, I may need to develop a couple of Device Drivers. I was wondering if anyone could point me to a document or a website that might help guide me to do this in the correction fashion.

To be a bit more specific, I have a custom UHS-II SD Card Host Controller which I would like to access through FAT and EXFAT commands. I am using a Zynq FPGA as a platform.

Thank you,

Jerrold