Hello. Typically this is done through some bus, where every connected board has it's own adress and all devices are put on bus, for example,this is can be RS485 physical interface and standart protocol such as Modbus RTU. All industrial automation are built on this conception. Once you have bus connected devices, you can connect them to anything that has underlying UART interface - to PC, Raspberi Pi, operator panel(HMI) , embedded mcu.