SW4STM32 and SW4Linux fully supports the STM32MP1 asymmetric multicore Cortex/A7+M4 MPUs

   With System Workbench for Linux, Embedded Linux on the STM32MP1 family of MPUs from ST was never as simple to build and maintain, even for newcomers in the Linux world.
And, if you install System Workbench for Linux in System Workbench for STM32 you can seamlessly develop and debug asymmetric applications running partly on Linux, partly on the Cortex-M4.
You can get more information from the ac6-tools website and download two short videos (registration required) highlighting:

System Workbench for STM32

Incorrect binary size after compilation.

I do not knwo if that is the best way to do it but I can tell you what your current linker is trying to do with the buffer ETH_DMADescTypeDef DMARxDscrTabETH_RXBUFNB

That buffer need to be in a fix memory location so in the linker file they created a memory sector Memory_B1(xrw)  : ORIGIN = 0x20010000, LENGTH = 0x80 , then almost at the end onf the linker they assing the section .RxDecripSection to sector Memory_B1 and since the previous declaration sets the buffer to the section .RxDecripSection then the buffer is set to address 0x20010000.

basically you are doing the same