Protocol specification for various device protocols in devices

# 📚 Docs or Wiki Bug Report

### Description [**REQUIRED**]
Is there any protocol specification(s) for the various device protocols in devices? For example, [Step #3 on this page](https://docs.edgexfoundry.org/2.1/examples/Ch-ExamplesAddingModbusDevice/#set-up-after-starting-services): shows some protocol information (Address, Port, UnitID, Timeout, IdleTimeout) for modbus-tcp. Where can I find the complete list of what can be specified in the various protocols in the device? For now, I'm looking for the lists for MQTT and Modbus.

## 🔬 Minimal Reproduction

### What's the affected URL? [**REQUIRED**]
https://docs.edgexfoundry.org/2.1/examples/Ch-ExamplesAddingModbusDevice/#set-up-after-starting-services

Start with the affected Modbus example page at the linked documentation URL and inspect the surrounding device-protocol documentation. Determine where protocol parameters for MQTT and Modbus are defined or described, then document the complete lists or link to authoritative specifications. Done means a newcomer can find the supported fields and understand what each parameter represents.

Written by the indexing model from the issue text.