applications: sdp: gpio: add README

Add simple readme for SDP GPIO application.

Signed-off-by: Marcin Szymczyk <[email protected]>

applications/sdp/gpio/README.rst

@@ -0,0 +1,35 @@
+.. _sdp_gpio:
+
+SDP GPIO
+########
+
+This application demonstrates how to create SDP on FLPR in Zephyr threadless mode by implementing a subset of Zephyr GPIO API.
+It is intended for use with Zephyr's :zephyr:code-sample:`blinky` sample.
+
+You can use the following IPC backends:
+
+* mbox (:kconfig:option:`SB_CONFIG_SDP_GPIO_BACKEND_MBOX`)
+* icmsg (:kconfig:option:`SB_CONFIG_SDP_GPIO_BACKEND_ICMSG`)
+* icbmsg (:kconfig:option:`SB_CONFIG_SDP_GPIO_BACKEND_ICBMSG`)
+
+Requirements
+************
+
+The firmware supports the following development kit:
+
+.. table-from-sample-yaml::
+
+Building and running
+********************
+
+You must include code for both the application core and FLPR core.
+The recommended method is to build the :zephyr:code-sample:`blinky` with the necessary sysbuild configuration.
+
+For example, to build with icmsg backend, run the following commands:
+
+  .. code-block:: console
+
+     west build -b nrf54l15dk/nrf54l15/cpuapp -- -DSB_CONFIG_PARTITION_MANAGER=n -DSB_CONFIG_SDP=y -DSB_CONFIG_SDP_GPIO=y -DSB_CONFIG_SDP_GPIO_BACKEND_ICMSG=y -DEXTRA_DTC_OVERLAY_FILE="./boards/nrf54l15dk_nrf54l15_cpuapp_egpio.overlay"
+     west flash
+
+Upon successful execution, **LED0** will start flashing.

doc/nrf/applications.rst

@@ -24,6 +24,7 @@ If you want to list applications available for one or more specific boards, `use
    ../../applications/nrf5340_audio/index
    ../../applications/nrf_desktop/README
    ../../applications/machine_learning/README
+   ../../applications/sdp/gpio/README
    ../../applications/serial_lte_modem/README
    ../../applications/matter_weather_station/README
    ../../applications/zigbee_weather_station/README