shields: Adding Adafruit INA228 Power Monitor.

This adds the shield definition for the Adafruit INA228 Power Monitor.
It connects to boards using the STEMMA-QT interface.

Product photo from https://learn.adafruit.com/assets/125551, with the
license CC BY-SA 3.0

Signed-off-by: Ian Wakely <raveious.irw@gmail.com>

Author: raveious

boards/shields/adafruit_ina228/Kconfig.shield

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+# Copyright (c) 2025 Ian Wakely
+# SPDX-License-Identifier: Apache-2.0
+
+config SHIELD_ADAFRUIT_INA228
+	def_bool $(shields_list_contains,adafruit_ina228)

boards/shields/adafruit_ina228/adafruit_ina228.overlay

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+/*
+ * Copyright (c) 2025 Ian Wakely
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+&zephyr_i2c {
+	status = "okay";
+
+	adafruit_ina228: ina228@40 {
+		compatible = "ti,ina228";
+		reg = <0x40>;
+		rshunt-micro-ohms = <15000>;
+		current-lsb-microamps = <10>;
+		status = "okay";
+	};
+};

boards/shields/adafruit_ina228/doc/adafruit_ina228.webp

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+.. _adafruit_ina228:
+
+Adafruit INA228 Shield
+#############################
+
+Overview
+********
+
+The `Adafruit INA228 High or Low Side Power Monitor`_ features the
+`TI INA228 current sensor`_, an I2C 20-bit power monitoring chip, with two
+STEMMA QT connectors. This board is capable of measuring up to 85VDC
+common-mode, high or low side measurements ranging from milli-amps to amps.
+
+.. figure:: adafruit_ina228.webp
+   :align: center
+   :alt: Adafruit INA228 Shield
+
+   Adafruit INA228 Shield (Credit: Adafruit)
+
+
+Requirements
+************
+
+This shield can be used with boards which provide an I2C connector, for
+example STEMMA QT or Qwiic connectors.
+The target board must define a ``zephyr_i2c`` node label.
+See :ref:`shields` for more details.
+
+
+Pin Assignments
+===============
+
++--------------+-------------------+
+| Shield Pin   | Function          |
++==============+===================+
+| SDA          | INA228 I2C SDA    |
++--------------+-------------------+
+| SCL          | INA228 I2C SCL    |
++--------------+-------------------+
+| ALRT         | INA228 ALERT out  |
++--------------+-------------------+
+| VIN-         | Current sense neg |
++--------------+-------------------+
+| VIN+         | Current sense pos |
++--------------+-------------------+
+| VBUS         | Voltage sense     |
++--------------+-------------------+
+
+See :dtcompatible:`ti,ina228` for documentation on how to adjust the
+devicetree file, for example to adjust the sample averaging.
+
+
+Programming
+***********
+
+Set ``--shield adafruit_ina228`` when you invoke ``west build``. For example
+when running the :zephyr:code-sample:`sensor_shell` sample:
+
+.. zephyr-app-commands::
+   :zephyr-app: samples/sensor/sensor_shell
+   :board: adafruit_qt_py_rp2040
+   :shield: adafruit_ina228
+   :goals: build
+
+.. _Adafruit INA228 High or Low Side Power Monitor:
+   https://learn.adafruit.com/adafruit-ina228-i2c-power-monitor/
+
+.. _TI INA228 Current sensor:
+   https://www.ti.com/product/INA228

boards/shields/adafruit_ina228/doc/index.rst

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+# SPDX-License-Identifier: Apache-2.0
+#
+# Copyright (c) 2025, Ian Wakely
+
+shield:
+  name: adafruit_ina228
+  full_name: Adafruit INA228 Power Monitor
+  vendor: adafruit
+  supported_features:
+    - sensor