ethtool development guidelines

I've attempted to condense my current opinions and rules for ethtool
development into a web page, for future reference:

https://www.kernel.org/pub/software/network/ethtool/devel.html

Hopefully this will save time for patch submitters and for me.

Ben.

-- 
Ben Hutchings, Senior Software Engineer, Solarflare
Not speaking for my employer; that's the marketing department's job.
They asked us to note that Solarflare product names are trademarked.