Support UART communication for Generic Hub (Linux to Baremetal/Zephyr)

[swayamshreemohanty]

Issue Description: I need to use the Hub Pattern over UART instead of TCP/IP.

My setup involves a Linux Raspberry Pi (running the Hub) communicating with remote microcontrollers (like STM32) running Zephyr or bare metal. The current example only covers network sockets.

Request:

Please add a reference implementation or configuration for using GenericHub with a UART driver.

Update the Hub APIs if needed to support serial byte streams better.

Ideally, include a basic example of a remote bare-metal/Zephyr node connecting to the Linux Hub via UART.