samples: boards: stm32: Add a sample to support ST BlueNRG GUI app

Introduce a sample for BlueNRG-based devices to support interaction with
ST BlueNRG GUI application based on U(S)ART protocol.

Signed-off-by: Ali Hozhabri <[email protected]>

samples/boards/stm32/bluetooth/interactive_gui/CMakeLists.txt

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+# SPDX-License-Identifier: Apache-2.0
+
+cmake_minimum_required(VERSION 3.20.0)
+
+find_package(Zephyr REQUIRED HINTS $ENV{ZEPHYR_BASE})
+project(st_interactive_gui)
+
+target_sources(app PRIVATE src/main.c)

samples/boards/stm32/bluetooth/interactive_gui/README.rst

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+.. _samples_boards_stm32_bluetooth_interactive-gui:
+.. zephyr:code-sample:: st_bluetooth_interactive_gui
+   :name: Bluetooth: ST Interactive GUI
+   :relevant-api: bluenrg_hci_driver bluetooth
+
+Expose ST BlueNRG Bluetooth network coprocessor over UART
+
+Overview
+*********
+
+Expose the Bluetooth network coprocessor via UART to a PC to be used
+with the ST BlueNRG GUI app. In this case, the main MCU becomes an intermediate level,
+and it passes the data between the host (PC) and controller.
+
+Requirements
+************
+
+* A board based on BlueNRG BLE module such as :ref:`disco_l475_iot1_board`
+* `BlueNRG GUI`_ application installed on your PC
+
+Default UART settings
+*********************
+
+It depends on the board default settings for ``zephyr,bt-c2h-uart`` DTS property.
+The UART default settings are:
+
+* Baudrate: 115200 bps
+* 8 bits, no parity, 1 stop bit
+
+Building and Running
+********************
+
+This sample can be found under :zephyr_file:`samples/boards/stm32/bluetooth/interactive_gui` in the
+Zephyr tree.
+
+.. _BlueNRG GUI:
+   https://www.st.com/en/embedded-software/stsw-bnrgui.html

samples/boards/stm32/bluetooth/interactive_gui/prj.conf

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+CONFIG_CONSOLE=n
+CONFIG_STDOUT_CONSOLE=n
+CONFIG_UART_CONSOLE=n
+CONFIG_SERIAL=y
+CONFIG_UART_INTERRUPT_DRIVEN=y
+CONFIG_BT=y
+CONFIG_BT_HCI_RAW=y
+CONFIG_BT_HCI_RAW_H4=y
+CONFIG_BT_HCI_RAW_H4_ENABLE=y
+CONFIG_BT_BUF_ACL_RX_SIZE=255
+CONFIG_BT_BUF_CMD_TX_SIZE=255
+CONFIG_BT_BUF_EVT_DISCARDABLE_SIZE=255
+CONFIG_BT_BLUENRG_ACI=n
+CONFIG_SYSTEM_WORKQUEUE_STACK_SIZE=512
+CONFIG_USB_DEVICE_INITIALIZE_AT_BOOT=y

samples/boards/stm32/bluetooth/interactive_gui/sample.yaml

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+sample:
+  name: Bluetooth ST Interactive GUI
+  description: Allows BlueNRG-based boards to connect to BlueNRG GUI application via UART
+tests:
+  sample.boards.stm32.bluetooth.interactive_gui:
+    harness: bluetooth
+    platform_allow:
+      - sensortile_box_pro
+      - disco_l475_iot1
+    tags:
+      - uart
+      - bluetooth