Is there any examples or documentation on loading the cortex-M4? For example, using u-boot or Linux rpmsg for communication? Is there SWD (serial wire debug)? (JTAG)?
You can use the cortex-m4 during compilation of you application with the proper flags for you compiler
The Cortex-M4 is another processor, is there documentation on how to use it?
Do you mean the always-on built-in M4 processor of A311D?
Yes, the goal is to load FreeRTOS and access I2C and DIO.