boards: shields: Introduce frdm_cr20a shield

Introduces an arduino-compatible shield for the mcr20a radio
transceiver.

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

boards/shields/frdm_cr20a/boards/frdm_k64f.conf

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+#
+# Copyright (c) 2019, NXP
+#
+# SPDX-License-Identifier: Apache-2.0
+#
+
+CONFIG_NET_L2_ETHERNET=n

boards/shields/frdm_cr20a/doc/index.rst

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+.. _frdm_cr20a_shield:
+
+NXP FRDM-CR20A
+##############
+
+Overview
+********
+
+The Freedom development board platform supports the MCR20A 2.4GHZ wireless
+transceiver. The FRDM-CR20A evaluation board is a small, low-power,
+cost-effective reference design for the MCR20A transceiver in a shield form
+factor, compatible with existing Freedom development platforms, such as
+:ref:`frdm_k64f`.
+
+.. image:: ./frdm_cr20a.jpg
+   :width: 720px
+   :align: center
+   :alt: FRDM-CR20A
+
+Hardware
+********
+
+- MCR20AVHM
+
+        - Low-power
+        - High-performance 2.4 GHz IEEE 802.15.4 compliant transceiver
+
+- Connectivity
+
+        - PCB inverted F-type antenna and SMA RF port
+        - Arduino compatible
+
+- Power Management
+
+        - Programmable output power -32 dBm to +8 dBm at the SMA connector, no trap
+        - Receiver sensitivity: –102 dBm, typical
+
+- Components
+
+        - Minimum number of matching components and external balun
+        - 1 RGB LED indicator
+        - 2 pushbutton switches
+
+For more information about the MCR20A SoC and FRDM-CR20A board:
+
+- `MCR20A Website`_
+- `MCR20A Datasheet`_
+- `MCR20A Reference Manual`_
+- `FRDM-CR20A Website`_
+- `FRDM-CR20A User Guide`_
+- `FRDM-CR20A Schematics`_
+
+Programming
+***********
+
+Set ``-DSHIELD=frdm_cr20a`` when you invoke ``west build`` or ``cmake`` in your
+Zephyr application. For example:
+
+.. zephyr-app-commands::
+   :zephyr-app: samples/net/wpanusb
+   :tool: all
+   :board: frdm_k64f
+   :shield: frdm_cr20a
+   :goals: build
+
+.. _FRDM-CR20A Website:
+   https://www.nxp.com/support/developer-resources/evaluation-and-development-boards/freedom-development-boards/wireless-connectivy/freedom-development-board-for-mcr20a-wireless-transceiver:FRDM-CR20A
+
+.. _FRDM-CR20A User Guide:
+   https://www.nxp.com/docs/en/user-guide/FRDMCR20AUG.pdf
+
+.. _FRDM-CR20A Schematics:
+   https://www.nxp.com/downloads/en/schematics/FRDM-CR20A-SCH.pdf
+
+.. _MCR20A Website:
+   https://www.nxp.com/products/wireless/thread/2.4-ghz-802.15.4-wireless-transceiver:MCR20A
+
+.. _MCR20A Datasheet:
+   https://www.nxp.com/docs/en/data-sheet/MCR20AVHM.pdf
+
+.. _MCR20A Reference Manual:
+   https://www.nxp.com/docs/en/reference-manual/MCR20RM.pdf

boards/shields/frdm_cr20a/frdm_cr20a.conf

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+#
+# Copyright (c) 2019, NXP
+#
+# SPDX-License-Identifier: Apache-2.0
+#
+
+CONFIG_IEEE802154_MCR20A=y
+CONFIG_NET_CONFIG_IEEE802154_DEV_NAME="mcr20a"
+
+CONFIG_GPIO=y
+CONFIG_SPI=y

boards/shields/frdm_cr20a/frdm_cr20a.overlay

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+/*
+ * Copyright (c) 2019, NXP
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+&arduino_spi {
+	status = "okay";
+
+	mcr20a@0 {
+		compatible = "nxp,mcr20a";
+		reg = <0x0>;
+		label = "mcr20a";
+		spi-max-frequency = <4000000>;
+		irqb-gpios = <&arduino_header 8 0>;	   /* D2 */
+		reset-gpios = <&arduino_header 11 0>;	   /* D5 */
+		status = "okay";
+	};
+};