[U-Boot] Rework the network stack

[Jörg Krause]

Hi all,

there is an issue with the current network stack using netconsole. It's
impossible to use network commands as TFTP inside netconsole, because
they try to run as atomic network commands.

The issue was already reported by Stefano Babic in 2010:
[U-Boot] NetConsole and network API
http://lists.denx.de/pipermail/u-boot/2010-August/075535.html

I run into the same problem:
[U-Boot] netconsole: USB Ethernet connection dropping with ping or
tftpboot
http://lists.denx.de/pipermail/u-boot/2015-February/203838.html

I have looked at the current network stack. The stack is based on the
concept of atomic network commands. The implementation for netconsole
looks very confusing.

Sascha Hauer has reimplemented the network stack for Barebox:
http://www.spinics.net/lists/u-boot-v2/msg00914.html

Looking at the current implementation of net.c looks very clean and
well-designed.

What do you think about porting this to U-Boot?

Best regards
Jörg Krause