doc: net: Enhance IEEE 802.15.4 documentation

Add a simple overview chapter to IEEE 802.15.4 documentation.

Signed-off-by: Jukka Rissanen <[email protected]>

Author: jukkar

doc/reference/networking/ieee802154.rst

@@ -5,7 +5,15 @@ IEEE 802.15.4
 
 Overview
 ********
-
+IEEE 802.15.4 is a technical standard which defines the operation of low-rate
+wireless personal area networks (LR-WPANs). For more detailed overview of this
+standard, see this
+`IEEE 802.15.4 Wikipedia article <https://en.wikipedia.org/wiki/IEEE_802.15.4>`_.
+
+Zephyr supports IEEE 802.15.4 with Thread and 6LoWPAN. The Thread implementation
+is based on `OpenThread <https://openthread.io/>`_.
+The IPv6 header compression in 6LoWPAN is shared with
+the Bluetooth IPSP (IP support profile).
 
 API Reference
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