doc: shields: nrf21540ek: no more explicit pin-forwarder shield

Update documentation regarding -DSHIELD=nrf21540ek.
This change is due to deprecation of explicit pin-forwarding
"pseudo shield".

Updated also the chapter "Enabling GPIO mode support for nRF21540"
to recommend uage of gpio forwarder.

Signed-off-by: Andrzej Kuros <[email protected]>

Author: ankuns

doc/nrf/app_dev/device_guides/fem/21540ek_dev_guide.rst

@@ -44,17 +44,29 @@ Alternatively, add the shield in the project's :file:`CMakeLists.txt` file:
 Building for a multicore board
 ==============================
 
-When building for a board with an additional network core, like the nRF5340, add the ``-DSHIELD`` variable with the *childImageName_* parameter between ``-D`` and ``SHIELD`` to build for the network core.
-In this case, the application core is only responsible for forwarding to the network core the pins needed to control the nRF21540 EK.
-The application core can be set up to forward the needed pins using the ``-DSHIELD=nrf21540ek`` setting.
-For example:
+When building for a board with an additional network core, like the nRF5340, add the ``-DSHIELD`` parameter to the command line:
 
-.. parsed-literal::
-   :class: highlight
+.. code-block:: console
+
+   west build -b nrf5340dk/nrf5340/cpuapp -- -DSHIELD=nrf21540ek
+
+In this case, the sysbuild will pass the *SHIELD=nrf21540ek* variable to all images that are built by the command.
+The build system will pick automatically appropriate overlay and configuration files for images for each core.
+Please note that the files are different for each of the cores.
+For the application core the overlay containing forwarding the FEM pins to the network core will be used.
+For the network core the overlay enabling nRF21540 FEM on the network core will be used.
+In case the application contains additional images for which the *SHIELD* variable should not be passed, you must pass manually the *SHIELD* variable to each relevant image build separately.
+
+.. code-block:: console
+
+   west build -b nrf5340dk/nrf5340/cpuapp -- -D<app_name_image>_SHIELD=nrf21540ek -Dipc_radio_SHIELD=nrf21540ek
 
-   west build -b nrf5340dk/nrf5340/cpuapp -- -DSHIELD=nrf21540ek -Dipc_radio_SHIELD=nrf21540ek
+In this case the *SHIELD=nrf21540ek* will be passed to the build of the *app_image_name* image for the application core.
+The build system will pick automatically an overlay file containing forwarding the FEM pins to the network core.
+The *SHIELD=nrf21540ek* variable will be passed to the build of the ``ipc_radio`` image for the network core.
+The build system will pick automatically an overlay file enabling nRF21540 FEM on the network core.
 
-In this command, the *childImageName_* parameter has the ``ipc_radio_`` value as default and builds the application with support for the combination of 802.15.4 and Bluetooth.
+In this command, the ``ipc_radio`` image us used as default and builds the network core image with support for the combination of 802.15.4 and Bluetooth.
 The ``ipc_radio`` has been used since the build system migration to sysbuild.
 See :ref:`Migrating to sysbuild <child_parent_to_sysbuild_migration>` page.
 Setting the correct sysbuild option enables support for 802.15.4 and Bluetooth :ref:`ipc_radio`.

doc/nrf/app_dev/device_guides/fem/fem_nrf21540_gpio.rst

@@ -51,18 +51,17 @@ To use nRF21540 in GPIO mode, complete the following steps:
 
    The state of the remaining control pins should be set in other ways and according to `nRF21540 Product Specification`_.
 
-#. On nRF53 devices, you must also apply the same devicetree node mentioned in **Step 1** to the network core  using sysbuild.
-   To apply the overlay to the correct network core child image, create an overlay file named :file:`sysbuild/*childImageName*/boards/nrf5340dk_nrf5340_cpunet.overlay` in your application directory, for example :file:`sysbuild/ipc_radio/boards/nrf5340dk_nrf5340_cpunet.overlay`.
-   For more information, see the :ref:`Migrating to sysbuild <child_parent_to_sysbuild_migration>` page.
+#. On nRF53 devices, the devicetree nodes described above must be added to the network core.
+   For the application core, you must also add a GPIO forwarder node to its devicetree file:
 
-   The *childImageName* default value is set to ``ipc_radio``:
+   .. code-block:: devicetree
 
-   ``ipc_radio`` represents all applications with support for the combination of both 802.15.4 and Bluetooth.
-   You can configure your application using the following sysbuild configurations:
-
-   * ``SB_CONFIG_NETCORE_IPC_RADIO=y`` for applications having support for 802.15.4, but not for Bluetooth.
-   * ``SB_CONFIG_NETCORE_IPC_RADIO_BT_HCI_IPC=y`` for application having support for Bluetooth, but not for 802.15.4.
-   * ``SB_CONFIG_NETCORE_IPC_RADIO=y`` and ``SB_CONFIG_NETCORE_IPC_RADIO_BT_HCI_IPC=y`` for multiprotocol applications having support for both 802.15.4 and Bluetooth.SB_CONFIG_NETCORE_IPC_RADIO=y`` and ``SB_CONFIG_NETCORE_IPC_RADIO_BT_HCI_IPC=y`` for multiprotocol applications having support for both 802.15.4 and Bluetooth.
+      &gpio_fwd {
+         nrf21540-gpio-if {
+            gpios = <&gpio0 13 0>,   /* tx-en-gpios */
+                    <&gpio0 14 0>,   /* rx-en-gpios */
+                    <&gpio0 15 0>;   /* pdn-gpios */
+         };
+      };
 
-   .. note::
-       This step is not needed when testing with :ref:`direct_test_mode` and :ref:`radio_test` on the nRF53 Series devices.
+   The pins defined in the GPIO forwarder node in the application core's devicetree file must match the pins defined in the FEM nodes in the network core's devicetree file.