boards: shields: add Mikroe RTC 18 Click shield

Add MikroElektronika RTC 18 Click shield support.

Signed-off-by: Dipak Shetty <[email protected]>

Author: dipakgmx

boards/shields/mikroe_rtc_18_click/Kconfig.shield

@@ -0,0 +1,5 @@
+# Copyright (c) 2025 Dipak Shetty
+# SPDX-License-Identifier: Apache-2.0
+
+config SHIELD_MIKROE_RTC_18_CLICK
+	def_bool $(shields_list_contains,mikroe_rtc_18_click)

boards/shields/mikroe_rtc_18_click/doc/index.rst

@@ -0,0 +1,48 @@
+.. _mikroe_rtc_18_click_shield:
+
+MikroElektronika RTC 18 Click
+#############################
+
+Overview
+********
+
+RTC 18 Click shield is built around the Micro Crystal **RV-3032-C7** temperature-compensated
+real-time clock (RTC) module.
+The module offers I²C communication, integrated timekeeping with leap year support, alarm and
+interrupt features, and a battery backup switchover circuit.
+
+The RTC is designed for high accuracy (≈ ±0.22 s/day) and extremely low power consumption, allowing
+it to retain time using a small backup battery when main supply is removed.
+
+More information about the shield can be found at
+`Mikroe RTC 18 click`_.
+
+.. figure:: rtc_18_click.webp
+   :align: center
+   :alt: MikroElektronika RTC 18 Click
+
+   MikroElektronika RTC 18 Click (Credit: MikroElektronika d.o.o.)
+
+Requirements
+************
+
+The shield uses a mikroBUS interface. The target board must define
+a ``mikrobus_i2c`` and ``mikrobus_header`` node labels
+(see :ref:`shields` for more details).
+
+Programming
+***********
+
+.. zephyr-app-commands::
+   :zephyr-app: samples/drivers/rtc/
+   :board: <board>
+   :shield: mikroe_rtc_18_click
+   :goals: build flash
+
+References
+**********
+
+.. target-notes::
+
+.. _Mikroe RTC 18 click:
+   https://www.mikroe.com/rtc-18-click

boards/shields/mikroe_rtc_18_click/doc/rtc_18_click.webp

@@ -0,0 +1,23 @@
+/*
+ * Copyright (c) 2025 Dipak Shetty
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+/ {
+	aliases {
+		rtc = &rv3032c_mikroe_rtc_18_click;
+	};
+};
+
+&mikrobus_i2c {
+	status = "okay";
+
+	rv3032c_mikroe_rtc_18_click: rv3032c@51 {
+		status = "okay";
+		compatible = "microcrystal,rv3032";
+		reg = <0x51>;
+		backup-switch-mode = "disabled";
+		clkout-frequency = <0>;
+		int-gpios = <&mikrobus_header 7 GPIO_ACTIVE_LOW>;
+	};
+};

boards/shields/mikroe_rtc_18_click/mikroe_rtc_18_click.overlay

@@ -0,0 +1,6 @@
+shield:
+  name: mikroe_rtc_18_click
+  full_name: RTC 18 Click
+  vendor: mikroe
+  supported_features:
+    - rtc