boards: shields: add microe eth3 click

Add shield definition for the Mikroe ETH 3 Click.
ETH 3 Click is a compact add-on board that contains
LAN9250 SPI Ethernet Controller

Signed-off-by: Mario Paja <mariopaja@hotmail.com>

boards/shields/mikroe_eth3_click/Kconfig.defconfig

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+# Copyright (c) 2024 Mario Paja
+# SPDX-License-Identifier: Apache-2.0
+
+if SHIELD_MIKROE_ETH3_CLICK
+
+if NETWORKING
+
+# LAN9250 is L2 chip slave on SPI
+config NET_L2_ETHERNET
+	default y
+
+endif # NETWORKING
+
+endif # SHIELD_MIKROE_ETH3_CLICK

boards/shields/mikroe_eth3_click/Kconfig.shield

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+# Copyright (c) 2024 Mario Paja
+# SPDX-License-Identifier: Apache-2.0
+
+config SHIELD_MIKROE_ETH3_CLICK
+	def_bool $(shields_list_contains,mikroe_eth3_click)

boards/shields/mikroe_eth3_click/doc/index.rst

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+.. _mikroe_eth3_click:
+
+MikroElektronika ETH 3 Click
+############################
+
+Overview
+********
+
+ETH 3 Click is an accessory board in mikroBus™ form factor. It features `LAN9250`_,
+a 10/100Mbps BASE-T stand alone Ethernet Controller with an on-board MAC & PHY,
+16Kbyte FIFO Buffer and SPI serial interface.
+More information at `ETH 3 Click Shield website`_.
+
+.. figure:: eth3_click.webp
+   :align: center
+   :alt: MikroElektronika ETH 3 Click
+
+   MikroElektronika ETH 3 Click (Credit: MikroElektronika)
+
+Pins Assignment of the Eth Click Shield
+=======================================
+
++-----------------------+---------------------------------------------+
+| Shield Connector Pin  | Function                                    |
++=======================+=============================================+
+| RST#                  | Ethernet Controller's Reset                 |
++-----------------------+---------------------------------------------+
+| CS#                   | SPI's Chip Select                           |
++-----------------------+---------------------------------------------+
+| SCK                   | SPI's ClocK                                 |
++-----------------------+---------------------------------------------+
+| SDO                   | SPI's Slave Data Output  (MISO)             |
++-----------------------+---------------------------------------------+
+| SDI                   | SPI's Slave Data Input   (MISO)             |
++-----------------------+---------------------------------------------+
+| INT                   | Ethernet Controller's Interrupt Output      |
++-----------------------+---------------------------------------------+
+
+
+Requirements
+************
+
+This shield can only be used with a board which provides a configuration
+for Mikro-BUS connectors and defines node aliases for SPI and GPIO interfaces
+(see :ref:`shields` for more details).
+
+Programming
+***********
+
+Set ``--shield mikroe_eth3_click`` when you invoke ``west build``. For example:
+
+.. zephyr-app-commands::
+   :zephyr-app: samples/net/dhcpv4_client
+   :board: mikroe_stm32_m4_clicker
+   :shield: mikroe_eth3_click
+   :goals: build
+
+References
+**********
+
+.. target-notes::
+
+.. _ETH 3 Click Shield website:
+   https://www.mikroe.com/eth-3-click
+
+.. _LAN9250:
+   https://www.microchip.com/en-us/product/lan9250

boards/shields/mikroe_eth3_click/mikroe_eth3_click.overlay

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+/* Copyright (c) 2024 Mario Paja
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+&mikrobus_spi {
+	status = "okay";
+
+	eth3_click_mikroe_eth3_click: eth3_click@0 {
+		compatible = "microchip,lan9250";
+		reg = <0x0>;
+		local-mac-address = [00 00 00 01 02 03];
+		spi-max-frequency = <30000000>;
+		int-gpios = <&mikrobus_header 7 GPIO_ACTIVE_LOW>;	/* INT */
+	};
+};