Use the new code-sample directive and roles to document the networking
samples so that they show up as "Related samples" when browsing the
various relevant networking APIs.
Signed-off-by: Benjamin Cabé <benjamin@zephyrproject.org>
Introduce EXTRA_CONF_FILE and EXTRA_DTC_OVERLAY_FILE and remove old
references to OVERLAY_CONFIG.
Signed-off-by: Torsten Rasmussen <Torsten.Rasmussen@nordicsemi.no>