Add CONFIG_NET_DHCPV4, which, after
https://github.com/zephyrproject-rtos/zephyr/pull/5750 works as follows:
static addresses are configured after boot, and DHCP requests are sent
at the same time. If valid DHCP reply is received, it overrides static
addresses.
This setup works out of the box for both direct connection to a
workstation (DHCP server usually is not available) and for connection
to a router (DHCP is available and required).
While this console API improves handling on real hardware boards
(e.g. clipboard paste is much more reliable, as well as programmatic
communication), it vice-versa poses problems under QEMU, apparently
because it doesn't emulate UART interrupt handling faithfully. That
leads to inability to run the testsuite on QEMU at all. To work that
around, we have to suuport both old and new console routines, and use
the old ones under QEMU.
Ideally, these should be configurable from Python (using network module),
but as that doesn't exist, we better off using Zephyr's native bootstrap
configuration facility.
This is to keep the top-level directory clean, to make it clear what is
core and what is a port, and to allow the repository to grow with new ports
in a sustainable way.