Adding OpenWrt support for Huawei hg8546m

Hello !

I'm the technical guy in a ISP, I every love the OpemWRT using for years...

To day we have 2.000 ONU modelo huawei hg8546m , we like to support openWRT...

But i don't have sure the ways...

First step for anything:

open the case, remove all heatsinks or covers on the board
record the model of every chip
identify the UART interface (4 pins or pinholes in a line)

also telling us the FCC ID helps

As a starter: https://openwrt.org/faq/how_can_i_add_support_for_a_new_device