[FS#390] Bt Home Hub 5 Type A Bridging Yellow Switch and RED Port does not work

[LEDE Bugs]

The following task has a new comment added:

FS#390 - Bt Home Hub 5 Type A Bridging Yellow Switch and RED Port does not work
User who did this - Mauro Mozzarelli (ezplanet)

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@Mathias

I do not want to test your staging tree because you refuse to listen to input and feedback and therefore it would be a waste of my time. You should try to be less hostile in your comments. 

I am very satisfied with the change I posted on lede-dev because it is simple, backward compatible and it does exactly what is required. The change applies only to BT Home Hub 5.

I attach the patch hereby to for those who want to get a working Red Ethernet and do not have access to lede-dev mailing list. The Red Ethernet will appear as "dmz" interface. The patch also allows to assign Red Ethernet (dmz port on the switch) to Switch 0.1 and extend the total number of "lan" interface ports to 5.

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More information can be found at the following URL:
https://bugs.lede-project.org/index.php?do=details&task_id=390#comment1718