[PATCH] package: add new poe-common package

[Sander Vanheule]

[Added the others back in Cc]

Hi Paul,

On Fri, 2024-01-26 at 00:00 +0100, Paul D wrote:
> 
> So, the power budget is a global option. Do we ever envisage that parts 
> of this budget can be concretely assigned to specific ports or more 
> abstract <board sections>?
> 
> e.g.
> 
>   	config port
>   		option name 'lan8'
>   		option id '1'
>   		option enable '1'
>   		option budget '15'

This would certainly be an option to extend the format. I'm not entirely sure where or how
the full supported format should be documented. The OpenWrt wiki seem to be where other
config files are documented, but I don't think we support documentation in our package
format.

Note that this package only intends to generate the bare minimum from information
contained in board.json, which is currently a list sorted by PSE output port. Following
the example config file:

        "poe" : ["lan8", "lan7", ... , "lan1"]

Board specific power constraints also belong in board.json. For a device with four 802.3af
ports (lan1-lan4) and four 802.3at ports (lan5-lan8) this could become:

	"poe" : {
		"lan1" : { "type" : "802.3af" },
		...
		"lan5" : { "type" : "802.3at" },
		...
	}

This could then be translated into a per-port "poe_type" property for example. We also
have some discussion going on this topic for the realtek-poe package [1].

1. https://github.com/Hurricos/realtek-poe/pull/31

Best,
Sander