Add network device to L4Linux

[Manolis Ragkousis]

Hello everyone,

Yesterday with Yang we found why adding the device tree caused the
L4linux boot to fail on Cubietruck with "failed to get physical address
for 2000000". I am sharing this here for future references in case
anyone needs it.

Yang was using the sun7i-a20-cubietruck.dts [1] device tree which is
normally supposed to be used by Linux running on bare-metal arm. In
L4Linux's case it's running on top of L4 which controls what L4linux can
see. As a result of using sun7i-a20-cubietruck.dts it tries to map a
physical address which it's not allowed to.

Using what Matthias described in [2], one needs to create a new device
tree based on the simple.dts inside l4linux-source/arch/l4/boot/dts/ and
add the information about the ethernet device and its dependencies
there. Also don't forget to write the io configuration for those devices.

Another mail from Matthias which serves as a really nice explanation of
the process is [3].

Thank you,
Manolis

[1]
http://elixir.free-electrons.com/u-boot/latest/source/arch/arm/dts/sun7i-a20-cubietruck.dts
[2] https://os.inf.tu-dresden.de/pipermail/l4-hackers/2016/007747.html
[3] https://os.inf.tu-dresden.de/pipermail/l4-hackers/2017/008069.html