Documentation: Add NuttX Web Panel documentation entry

This commits adds an example of the NuttX Web Panel documentation
along with its usage on ESP32-P4.

Signed-off-by: Tiago Medicci Serrano <tiago.medicci@espressif.com>

Documentation/applications/examples/webpanel/index.rst

@@ -0,0 +1,112 @@
+.. _nuttx-webpanel:
+
+====================================
+``webpanel`` NuttX Web Panel
+====================================
+
+This guide explains how to run the NuttX Web Panel.
+
+The NuttX Web Panel is a self-hosted web interface for device management. It
+provides a browser-based dashboard with system information, an NSH terminal,
+file management on SmartFS, and network configuration. The application is
+implemented in ``apps/examples/webpanel/`` and is inspired by consumer IoT
+management panels.
+
+.. figure:: nuttx-webpanel-home.png
+   :align: center
+   :alt: NuttX Web Panel home page on ESP32-P4
+
+   NuttX Web Panel home page on ESP32-P4 (``esp32p4-function-ev-board:webpanel``)
+
+How Does it Work?
+=================
+
+The web panel combines several NuttX components:
+
+1. **THTTPD** serves static HTML/CSS/JavaScript from a ROMFS image mounted at
+   ``/data/www``.
+2. **BINFS** and **UNIONFS** expose built-in CGI programs under
+   ``/data/www/cgi-bin`` for dynamic requests (system info, file listing,
+   upload, and DHCP renew).
+3. **libwebsockets** provides a WebSocket server (TCP port 8080) that spawns
+   an NSH session over a POSIX pseudo-terminal for the browser terminal.
+4. **mDNS** advertises the HTTP service as ``webpanel.local`` (``_http._tcp``
+   on port 80). The ``mdnsd_event`` application starts the mDNS daemon when
+   an IP address is assigned.
+5. **SmartFS** on SPI flash (mounted at ``/mnt``) stores user files, including
+   uploaded Python scripts.
+
+On boot, ``/etc/init.d/rcS`` (enabled via ``CONFIG_ETC_ROMFS``) sets the
+hostname to ``webpanel``, starts ``webpanel`` in the background, and launches
+``mdnsd_event`` to register the HTTP service once DHCP completes.
+
+Building and Running the Web Panel
+==================================
+
+ESP32-P4-Function-EV-Board
+--------------------------
+
+For this example, use the ESP32-P4-Function-EV-Board with Ethernet connected
+to the board PHY port. The ``esp32p4-function-ev-board:webpanel`` defconfig
+requires **16 MB** flash (see ``CONFIG_ESPRESSIF_FLASH_16M``).
+
+This defconfig includes the CPython interpreter and produces a large firmware
+image. A full clean build may take several minutes.
+
+Build and flash the board with the following commands:
+
+.. code:: console
+
+   $ cd nuttx
+   $ make distclean
+   $ ./tools/configure.sh esp32p4-function-ev-board:webpanel
+   $ make -j$(nproc) flash ESPTOOL_PORT=/dev/ttyACM0
+
+On **v1.5.2**, use ``/dev/ttyACM0`` (USB Serial/JTAG) for flashing. UART0
+(GPIO37/GPIO38) remains the serial console; attach an external USB-to-UART
+adapter to monitor NSH while the web panel runs.
+
+After flashing, connect the Ethernet cable and wait for DHCP. Then open a browser
+on the same LAN:
+
+.. code:: text
+
+   http://webpanel.local
+
+If mDNS is unavailable, check the assigned address on the serial console:
+
+.. code:: console
+
+   nsh> ifconfig
+   eth0    Link encap:Ethernet HWaddr 30:ed:a0:ec:f1:60 at RUNNING mtu 1500
+           inet addr:10.0.10.50 DRaddr:10.0.10.1 Mask:255.255.255.0
+
+and browse to ``http://<inet-addr>`` instead.
+
+The interface provides four sections:
+
+* **Home** — live system and network information
+* **Terminal** — browser NSH shell over WebSocket
+* **Files** — browse, upload, and run scripts on ``/mnt``
+* **Network** — interface details and DHCP lease renewal
+
+Python scripts can be uploaded through the **Files** tab and executed from the
+**Terminal** tab or via the **Run** button for ``.py`` files. See also the
+:doc:`Python Interpreter </applications/interpreters/python/index>` page.
+
+Configuration
+=============
+
+The web panel is enabled with ``CONFIG_EXAMPLES_WEBPANEL``. The defconfig also
+enables the dependencies selected by that option, including THTTPD,
+libwebsockets (server mode), BINFS, UNIONFS, and pseudo-terminal support.
+
+Key Kconfig options (under ``Application Configuration`` →
+``Examples`` → ``Web Panel for device management``):
+
+* ``CONFIG_EXAMPLES_WEBPANEL_NETIF`` — network interface name (default
+  ``eth0``)
+* ``CONFIG_EXAMPLES_WEBPANEL_WS_PORT`` — WebSocket terminal port (default
+  ``8080``)
+* ``CONFIG_EXAMPLES_MDNS_SERVICE`` / ``CONFIG_EXAMPLES_MDNS_SERVICE_PORT`` —
+  mDNS service type and port advertised by ``mdnsd_event``

Documentation/platforms/risc-v/esp32p4/boards/esp32p4-function-ev-board/index.rst

@@ -483,6 +483,12 @@ watchdog
 
 Demonstrates MWDT/RWDT watchdog timers via the ``wdog`` app.
 
+webpanel
+--------
+
+This configuration enables the NuttX Web Panel for ESP32-P4.
+Please refer to the :doc:`Web Panel </applications/examples/webpanel/index>` page.
+
 Related Documentation
 =====================