pm: device: Add power domain get function

Add a function to get power domain device from a pm device.
Prompted by need to run runtime usage checks on pd from pm device.

Signed-off-by: Jacob McClellan <[email protected]>

include/zephyr/pm/device.h

@@ -577,6 +577,16 @@ bool pm_device_wakeup_is_capable(const struct device *dev);
  */
 bool pm_device_on_power_domain(const struct device *dev);
 
+/**
+ * @brief Get the device's power domain.
+ *
+ * @param dev Device instance.
+ *
+ * @retval pd The device's power domain if on a power domain
+ * @retval NULL if not on a power domain
+ */
+const struct device *pm_device_get_power_domain(const struct device *dev);
+
 /**
  * @brief Add a device to a power domain.
  *

subsys/pm/device.c

@@ -338,6 +338,19 @@ bool pm_device_on_power_domain(const struct device *dev)
 #endif
 }
 
+const struct device *pm_device_get_power_domain(const struct device *dev)
+{
+#ifdef CONFIG_PM_DEVICE_POWER_DOMAIN
+	if (pm_device_on_power_domain(dev) == false) {
+		return NULL;
+	}
+	return dev->pm_base->domain;
+#else
+	ARG_UNUSED(dev);
+	return NULL;
+#endif
+}
+
 bool pm_device_is_powered(const struct device *dev)
 {
 #ifdef CONFIG_PM_DEVICE_POWER_DOMAIN