I am willing to design my own home computer. It has long been a dream since the 90s and my C64. At the moment it seems to be a good decision to use a STM32MP157. All of the needed periphials are on the the chip. But I want to build expansion slots á la ISA, PCI or something similar with expansion slots, so that I can add another GFX-Card, network card, sound card etc.
But all I can find about ARM cores and expansion seems to be AXI and the sentence "AXI is just a protocol". How can I create an expansion bus/infrastructure from AXI with physical connectors. I will need access to DMA, the memory with the periphials plugedinto those slots. I know the question is (very) vague but I have to start somewhere. :)