[FPGA Board Fundamentals] Implementing opentitan on other boards(not CW310)

### Description

I cannot obtain the CW310 board, but I want to implement opentitan on the existing board and test it.I am currently loading bitstream into my FPGA and using UART_ The USB chip received a message from Opentitan.I found an error while running the command to load the program into opnetitan. I feel it's a hardware issue. After reviewing the schematic diagram of the CW310 board, I found that there are many interface connections between SAM3X and Opentitan. After browsing the relevant issues posted on the Github website, I feel that this SAM3X microcontroller is indispensable.
what is the function of the SAM3X microcontroller? I couldn't find any relevant introduction on Opentitan's website.
 I feel that for future testing, I need to add a PCB with SAM3X to my FPGA board. And connect the pins of this MCU with some necessary pins of the opentitan to achieve loading of the opentitan program and other things. 
What else do I need to do in order to conduct opentitan experiments on my existing board?


Start by reviewing the CW310 schematic and the reported FPGA bitstream and UART-loading behavior, then identify which SAM3X connections OpenTitan relies on. A useful outcome would document the hardware and board-support requirements for running experiments on the existing FPGA board.

Written by the indexing model from the issue text.