doc: move networking to connectivity

Create a new section 'Connectivity' and move Networking guides and API
docs to this new section.

Signed-off-by: Anas Nashif <anas.nashif@intel.com>

doc/connectivity/networking/api/dhcpv4.rst

@@ -0,0 +1,31 @@
+.. _dhcpv4_interface:
+
+DHCPv4
+######
+
+.. contents::
+    :local:
+    :depth: 2
+
+Overview
+********
+
+The Dynamic Host Configuration Protocol (DHCP) is a network management protocol
+used on IPv4 networks. A DHCPv4 server dynamically assigns an IPv4 address
+and other network configuration parameters to each device on a network so they
+can communicate with other IP networks.
+See this
+`DHCP Wikipedia article <https://en.wikipedia.org/wiki/Dynamic_Host_Configuration_Protocol>`_
+for a detailed overview of how DHCP works.
+
+Note that Zephyr only supports DHCP client functionality.
+
+Sample usage
+************
+
+See :ref:`dhcpv4-client-sample` for details.
+
+API Reference
+*************
+
+.. doxygengroup:: dhcpv4