arm: stm32h7: Support for the STM32H747I-DISCO board

[Johannes (krjdev) Krottmayer]

Hi,

I want add support for STM32H747I-DISCO from STMicroelectronics,
for the purpose of education. Want to use U-Boot as boot-loader
for my projects.

Here you the official website from the board:
https://www.st.com/en/evaluation-tools/stm32h747i-disco.html

But there some issues on the website:
- According the website, the board has 256Mbit external SDRAM

That's not true. There is a 512MBit SDRAM from ISSI mounted.

Can I release a patch series here, when my work is done? I don't
know if there any interest for other users exists, to add here
the support to U-Boot.

Currently creating the device-trees for the SoC and the board.
But must at least modify (fix) the drivers for the board:

drivers/clk/clk_stm32h7.c has some issues in the probe function:

The endless loop of dead, without a timeout when reading the
registers on some possible condition, without warn the user
(put some error messages and call the hang function).

Kind regards,

Johannes K.