Document make-cross-ovs helper script (#277)

Signed-off-by: Derek G Foster <[email protected]>

docs/scripts/helper-scripts.rst

@@ -3,10 +3,21 @@
 
 ==============
 Helper Scripts
-==============   
+==============
+
+Build
+-----
 
 .. toctree::
    :maxdepth: 1
 
    make-all
+
+ES2K Build
+----------
+
+.. toctree::
+   :maxdepth: 1
+
+   make-cross-ovs
    config-cross-recipe

docs/scripts/make-cross-ovs.rst

@@ -0,0 +1,98 @@
+.. Copyright 2023 Intel Corporation
+   SPDX-License-Identifier: Apache 2.0
+
+=================
+make-cross-ovs.sh
+=================
+
+Helper script to cross-compile and install Open vSwitch for the Arm Compute
+Complex (ACC) of the Intel® IPU E2100.
+
+Build flow
+==========
+
+Building and installing OVS is the first step in building P4 Control Plane
+for the IPU E2100.
+
+.. image:: make-cross-ovs-flow.png
+
+Once OVS is built, you can use the ``config-cross-recipe.sh`` script to
+configure the next stage of the build, and the ``cmake`` command to compete it.
+
+Syntax
+======
+
+.. code-block:: text
+
+  ./scripts/es2k/make-cross-ovs.sh \
+      [--help|-h]  \
+      [--dry-run|-n] \
+      [--build=BLDDIR | -B BLDDIR] \
+      [--prefix=PREFIX | -P PREFIX] \
+      [--toolchain=TOOLFILE | -T TOOLFILE ] \
+      [--jobs=NJOBS | -j NJOBS]
+
+Command-line parameters
+=======================
+
+General
+-------
+
+``--dry-run``, ``-n``
+  Displays the parameters that will be passed to CMake, and exits.
+
+``--help``, ``-h``
+  Displays usage information and exits.
+
+Paths
+-----
+
+``--build=BLDDIR``, ``-B BLDDIR``
+  Directory that CMake will use to perform the build.
+  Will be created if it does not exist.
+
+  Specifies the value of the ``-B`` CMake option.
+  Can be used to create separate build directories for native and
+  cross-compiled builds.
+  Defaults to ``ovs/build``.
+
+``--prefix=PREFIX``, ``-P PREFIX`` *(see note)*
+  Directory in which OVS will be installed.
+  Will be created if it does not exist.
+
+  Specifies the value of the ``CMAKE_INSTALL_PREFIX`` variable when
+  building P4 Control Plane.
+  Defaults to ``//opt/ovs``.
+
+``--toolchain=FILE``, ``-T FILE``
+  Path to the CMake toolchain file.
+
+  Specifies the value of the ``CMAKE_TOOLCHAIN_FILE`` variable.
+  Defaults to the value of the ``CMAKE_TOOLCHAIN_FILE`` environment
+  variable.
+
+.. note::
+  ``//`` at the beginning of the directory path will be replaced with
+  the *sysroot* directory path.
+
+Options
+-------
+
+``--jobs=NJOBS``, ``-j NJOBS``
+  Number of build threads.
+
+  Specifies the value of the ``-j`` CMake option.
+  Defaults to 8 threads.
+
+Environment variables
+=====================
+
+``CMAKE_TOOLCHAIN_FILE``
+  Path to the CMake toolchain file to be used.
+  Specifies the value of the ``CMAKE_TOOLCHAIN_FILE`` variable.
+  May be overridden by ``--toolchain=TOOLFILE``.
+  Must be defined.
+
+``SDKTARGETSYSROOT``
+  Path to the system root (*sysroot*) directory for the ACC.
+  Must be defined.