How is modbus_rx_handler in modbus_core.c triggered by the kernel?

[TK5090]

Hi everyone,

I'm analyzing the file modbus_core.c and noticed that the function modbus_rx_handler appears to be invoked by the kernel, but it's not immediately clear how this happens under the hood.

A few specific questions:

1. How is modbus_rx_handler registered or linked into the system so that it gets called by the kernel?

2. Is it tied to an interrupt or callback mechanism, such as via a UART or DMA receive interrupt?

3. It seems that the handler is only invoked when data is actually sent to the Modbus device. Is this correct? Or are there edge cases where it might be called in other contexts as well?

4. Is it possible to delay the invocation of modbus_rx_handler or triggering the sending the data back to modbus client by a user defined delay length and not through a KConfig Config?

Any clarification on the internal flow or pointers to where this linkage happens would be appreciated.

Thanks!