boards: Introduce frdm_kw41z ble controller shield

The frdm_kw41z can be used as a standalone board or as an arduino
shield. Zephyr already supports the standalone configuration, this
change introduces support the arduino shield configuration.

In the arduino configuration, the frdm_kw41z operates as a ble
controller over serial hci. It can be attached to another board, such as
the frdm_k64f or mimxrt1050_evk, which runs the ble host.

Signed-off-by: Maureen Helm <maureen.helm@nxp.com>

boards/shields/frdm_kw41z/Kconfig.shield

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+#
+# Copyright (c) 2018, NXP
+#
+# SPDX-License-Identifier: Apache-2.0
+#
+
+config SHIELD_FRDM_KW41Z
+	bool "frdm_kw41z"

boards/shields/frdm_kw41z/doc/frdm_kw41z.rst

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+.. _frdm_kw41z_shield:
+
+NXP FRDM-KW41Z
+##############
+
+Overview
+********
+
+The FRDM-KW41Z is a development kit enabled by the Kinetis |reg| W series
+KW41Z/31Z/21Z (KW41Z) family built on ARM |reg| Cortex |reg|-M0+ processor with
+integrated 2.4 GHz transceiver supporting Bluetooth |reg| Smart/Bluetooth
+|reg| Low Energy
+(BLE) v4.2, Generic FSK, IEEE |reg| 802.15.4 and Thread.
+
+The FRDM-KW41Z can be used as a standalone board or as an Arduino shield. This
+document covers usage as a shield; see :ref:`frdm_kw41z` for usage as a
+standalone board.
+
+Bluetooth Controller
+********************
+
+To use the FRDM-KW41Z as a Bluetooth low energy controller shield with a serial
+host controller interface (HCI):
+
+#. Download the MCUXpresso SDK for FRDM-KW41Z from the `MCUXpresso SDK Builder
+   Website`_.
+
+#. Open the MCUXpresso IDE or IAR project in
+   :file:`boards/frdmkw41z/wireless_examples/bluetooth/hci_black_box/bm`
+
+#. Open :file:`source/common/app_preinclude.h` and add the following line:
+
+.. code-block:: console
+
+	#define gSerialMgrRxBufSize_c 64
+
+#. Build the project to generate a binary :file:`hci_black_box_frdmkw41z.bin`.
+
+#. Connect the FRDM-KW41Z board to your computer with a USB cable. A USB mass
+   storage device should enumerate.
+
+#. Program the binary to flash by copying it to the USB mass storage device.
+
+#. Remove the USB cable to power down the board.
+
+#. Configure the jumpers J30 and J31 such that:
+   - J30 pin 1 is attached to J31 pin 2
+   - J30 pin 2 is attached to J31 pin 1
+   The jumpers should be parallel to the Arduino headers. This configuration
+   routes the UART RX and TX signals to the Arduino header, rather than to the
+   OpenSDA circuit.
+
+#. Attach the FRDM-KW41Z to the Arduino header on your selected main board,
+   such as :ref:`mimxrt1050_evk` or :ref:`frdm_k64f`.
+
+#. Set CONFIG_SHIELD_FRDM_KW41Z=y in your Zephyr bluetooth application.
+
+References
+**********
+
+.. target-notes::
+
+.. _MCUXpresso SDK Builder Website:
+   https://mcuxpresso.nxp.com

boards/shields/frdm_kw41z/frdm_kw41z.overlay

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+/*
+ * Copyright (c) 2018, NXP
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+/ {
+	chosen {
+		zephyr,bt-uart = &arduino_serial;
+	};
+};
+
+&arduino_serial {
+	status = "ok";
+	current-speed = <115200>;
+};