legacy-networking: Add note with build instructions for rtems-net-legacy

legacy-networking/index.rst

@@ -22,6 +22,7 @@ RTEMS Legacy Network User Manual (|version|).
 	:numbered:
 
 	preface
+	quick_start
 	network_task_structure
 	networking_driver
 	using_networking_rtems_app

legacy-networking/quick_start.rst

@@ -0,0 +1,33 @@
+.. SPDX-License-Identifier: CC-BY-SA-4.0
+
+Quick Start
+#######
+
+This legacy networking is now a standalone repository and needs to be built
+separately.
+
+The repository can be found here: https://git.rtems.org/rtems-net-legacy/
+
+There's an RSB recipe to build rtems-net-legacy. Here's an example of building
+rtems-net-legacy using RSB for powerpc/beatnik BSP with rtems version 6:
+
+  .. code-block:: shell
+
+        ../source-builder/sb-set-builder \
+        --prefix=/path/to/rtems/prefix \
+        6/rtems-net-legacy \
+        --host=powerpc-rtems6 \
+        --with-rtems-bsp=beatnik
+
+Manually building the rtems-net-legacy repo:
+
+  .. code-block:: shell
+
+        git submodule init
+        git submodule update
+        ./waf configure --prefix=/path/to/rtems/prefix
+        ./waf
+        ./waf install
+
+Please refer to README.waf in rtems-net-legacy repository for more details on
+using waf with legacy networking.