boards: shields: Add support for X-NUCLEO-BNRG2A1 shield

Add support for X-NUCLEO-BNRG2A1 which is a BLE expansion board based on
the BLUENRG-M2SP.

Signed-off-by: Ali Hozhabri <ali.hozhabri@st.com>

boards/shields/x_nucleo_bnrg2a1/Kconfig.defconfig

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+# Copyright (c) 2024 STMicroelectronics
+# SPDX-License-Identifier: Apache-2.0
+
+if SHIELD_X_NUCLEO_BNRG2A1
+
+if BT
+
+config SPI
+	default y
+
+choice BT_HCI_BUS_TYPE
+	default BT_SPI
+endchoice
+
+config BT_BLUENRG_ACI
+	default y
+
+# Disable Flow control
+config BT_HCI_ACL_FLOW_CONTROL
+	default n
+
+endif # BT
+
+endif # SHIELD_X_NUCLEO_BNRG2A1

boards/shields/x_nucleo_bnrg2a1/Kconfig.shield

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+# Copyright (c) 2024 STMicroelectronics
+# SPDX-License-Identifier: Apache-2.0
+
+config SHIELD_X_NUCLEO_BNRG2A1
+	def_bool $(shields_list_contains,x_nucleo_bnrg2a1)

boards/shields/x_nucleo_bnrg2a1/doc/index.rst

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+.. _x-nucleo-bnrg2a1:
+
+X-NUCLEO-BNRG2A1: BLE expansion board
+#####################################
+
+Overview
+********
+The X-NUCLEO-BNRG2A1 is a Bluetooth Low Energy evaluation board based on the
+BlueNRG-M2SP RF module to allow expansion of the STM32 Nucleo boards.
+The BlueNRG-M2SP module is FCC (FCC ID: S9NBNRGM2SP) and IC certified
+(IC: 8976C-BNRGM2SP).
+
+The X-NUCLEO-BNRG2A1 is compatible with the ST Morpho and Arduino UNO R3
+connector layout (the user can mount the ST Morpho connectors, if required). The
+X-NUCLEO-BNRG2A1 interfaces with the host microcontroller via the SPI pins, and
+the user can change the default SPI clock, the SPI chip select and SPI IRQ by
+changing either one resistor or jumper on the evaluation board.
+
+Note : This shield is compatible out of the box with Arduino UNO R3 connectors,
+but CS signal is not the standard Arduino SPI_CS signal.
+Please refer to "Hardware configuration" section.
+
+.. image:: img/x-nucleo-bnrg2a1.webp
+     :align: center
+     :alt: X-NUCLEO-BNRG2A1
+
+More information about the board can be found at the
+`X-NUCLEO-BNRG2A1 website`_.
+
+Hardware configuration
+**********************
+
+Out of the box, X-NUCLEO-BNRG2A1 shield expects SPI CS to be available on
+Arduino pin A1 instead of usual Arduino UNO R3 SPI CS D10.
+This is not a problem as CS signal is software driven gpio on Arduino A1
+see cs-gpios in x_nucleo_bnrg2a1.overlay
+
+Shield configuration could be modified by moving resistors or changing jumper as
+follows:
+
+ - SPI SCK: to use D3 instead of D13, short J14 pins 2 and 3
+
+Additionally, depending on your host board, some modifications of the BLE
+expansion board could be made:
+
+ - CS: To use D1 instead of A1, unmount R76 and mount R86
+
+nucleo_l476rg does not need hardware modifications.
+
+Hardware
+********
+
+X-NUCLEO-BNRG2A1 provides a BlueNRG-M2SP chip with the following key features:
+
+ - Bluetooth v5.2 compliant
+ - Embedded BALF-NRG-02D3 integrated matched balun with harmonic filter
+ - BLE data packet length extension
+
+More information about X-NUCLEO-BNRG2A1 can be found here:
+       - `X-NUCLEO-BNRG2A1 databrief`_
+
+Programming
+***********
+
+You can use the X-NUCLEO-BNRG2A1 as a Bluetooth Low-Energy controller
+shield with an SPI host controller interface (HCI-SPI).  Activate the presence
+of the shield for the project build by adding the ``-DSHIELD`` arg to the
+build command:
+
+ .. zephyr-app-commands::
+    :zephyr-app: your_app
+    :board: your_board_name
+    :shield: x_nucleo_bnrg2a1
+    :goals: build
+
+Alternatively, set use of this shield in the project's ``CMakeLists.txt`` file:
+
+.. code-block:: cmake
+
+	set(SHIELD x_nucleo_bnrg2a1)
+
+References
+**********
+
+.. target-notes::
+
+.. _X-NUCLEO-BNRG2A1 website:
+   https://www.st.com/en/ecosystems/x-nucleo-bnrg2a1.html
+
+.. _X-NUCLEO-BNRG2A1 databrief:
+   https://www.st.com/resource/en/data_brief/x-nucleo-bnrg2a1.pdf

boards/shields/x_nucleo_bnrg2a1/x_nucleo_bnrg2a1.overlay

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+/*
+ * Copyright (c) 2024 STMicroelectronics
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+&arduino_spi {
+	cs-gpios = <&arduino_header 1 GPIO_ACTIVE_LOW>;	/* A1 */
+
+	bluenrg-2@0 {
+		compatible = "st,hci-spi-v2";
+		reg = <0>;
+		reset-gpios = <&arduino_header 13 GPIO_ACTIVE_LOW>;  /* D7 */
+		irq-gpios = <&arduino_header 0 (GPIO_ACTIVE_HIGH | GPIO_PULL_DOWN)>;  /* A0 */
+		spi-cpha; /* CPHA=1 */
+		spi-hold-cs;
+		spi-max-frequency = <DT_FREQ_M(1)>;
+		reset-assert-duration-ms = <6>;
+	};
+};