of/i2c: implement of_find_i2c_adapter_by_node

This finds the struct i2c_adapter * for a given device tree node. Just
like of_find_i2c_device_by_node.

Signed-off-by: Stephen Warren <swarren@nvidia.com>
Signed-off-by: Wolfram Sang <w.sang@pengutronix.de>

drivers/of/of_i2c.c

@@ -94,4 +94,18 @@ struct i2c_client *of_find_i2c_device_by_node(struct device_node *node)
 }
 EXPORT_SYMBOL(of_find_i2c_device_by_node);
 
+/* must call put_device() when done with returned i2c_adapter device */
+struct i2c_adapter *of_find_i2c_adapter_by_node(struct device_node *node)
+{
+	struct device *dev;
+
+	dev = bus_find_device(&i2c_bus_type, NULL, node,
+					 of_dev_node_match);
+	if (!dev)
+		return NULL;
+
+	return i2c_verify_adapter(dev);
+}
+EXPORT_SYMBOL(of_find_i2c_adapter_by_node);
+
 MODULE_LICENSE("GPL");