spmi: add a helper to look up an SPMI device from a device node

The helper function spmi_device_from_of() takes a device node and
returns the SPMI device associated with it.
This is like of_find_device_by_node but for SPMI devices.
Signed-off-by: Caleb Connolly <caleb.connolly@linaro.org>
Acked-by: Stephen Boyd <sboyd@kernel.org>
Link: https://lore.kernel.org/r/20220429220904.137297-2-caleb.connolly@linaro.orgSigned-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

drivers/spmi/spmi.c

@@ -386,6 +386,23 @@ static struct bus_type spmi_bus_type = {
 	.uevent		= spmi_drv_uevent,
 };
 
+/**
+ * spmi_device_from_of() - get the associated SPMI device from a device node
+ *
+ * @np:		device node
+ *
+ * Returns the struct spmi_device associated with a device node or NULL.
+ */
+struct spmi_device *spmi_device_from_of(struct device_node *np)
+{
+	struct device *dev = bus_find_device_by_of_node(&spmi_bus_type, np);
+
+	if (dev)
+		return to_spmi_device(dev);
+	return NULL;
+}
+EXPORT_SYMBOL_GPL(spmi_device_from_of);
+
 /**
  * spmi_controller_alloc() - Allocate a new SPMI device
  * @ctrl:	associated controller

include/linux/spmi.h

@@ -164,6 +164,9 @@ static inline void spmi_driver_unregister(struct spmi_driver *sdrv)
 	module_driver(__spmi_driver, spmi_driver_register, \
 			spmi_driver_unregister)
 
+struct device_node;
+
+struct spmi_device *spmi_device_from_of(struct device_node *np);
 int spmi_register_read(struct spmi_device *sdev, u8 addr, u8 *buf);
 int spmi_ext_register_read(struct spmi_device *sdev, u8 addr, u8 *buf,
 			   size_t len);