device: Add find_dev_nested_path helper function

Add find_dev_nested_path helper function to simplify finding deeply
nested devices.

BUG=b:157580724
TEST=Find bluetooth device on dalboz

Change-Id: I48fa5fcad0030fb6dcea97b9fc76e1d3d3f9b28f
Signed-off-by: Rob Barnes <robbarnes@google.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/43776
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Furquan Shaikh <furquan@google.com>
Reviewed-by: Raul Rangel <rrangel@chromium.org>

src/device/device_const.c

@@ -196,6 +196,33 @@ DEVTREE_CONST struct device *find_dev_path(
 	return child;
 }
 
+/**
+ * Find the device structure given an array of nested device paths,
+ *
+ * @param parent The parent bus to start the search on.
+ * @param nested_path An array of relative paths from the parent bus to the target device.
+ * @param nested_path_length Number of path elements in nested_path array.
+ * @return Pointer to a device structure for the device at nested path
+ *         or 0/NULL if no device is found.
+ */
+DEVTREE_CONST struct device *find_dev_nested_path(
+	const struct bus *parent, const struct device_path nested_path[],
+	size_t nested_path_length)
+{
+	DEVTREE_CONST struct device *child;
+
+	if (!parent || !nested_path || !nested_path_length)
+		return NULL;
+
+	child = find_dev_path(parent, nested_path);
+
+	/* Terminate recursion at end of nested path or child not found */
+	if (nested_path_length == 1 || !child)
+		return child;
+
+	return find_dev_nested_path(child->link_list, nested_path + 1, nested_path_length - 1);
+}
+
 DEVTREE_CONST struct device *pcidev_path_behind(
 	const struct bus *parent, pci_devfn_t devfn)
 {

src/include/device/device.h

@@ -207,6 +207,10 @@ void run_bios(struct device *dev, unsigned long addr);
 DEVTREE_CONST struct device *find_dev_path(
 		const struct bus *parent,
 		const struct device_path *path);
+DEVTREE_CONST struct device *find_dev_nested_path(
+		const struct bus *parent,
+		const struct device_path nested_path[],
+		size_t nested_path_length);
 struct device *alloc_find_dev(struct bus *parent, struct device_path *path);
 struct device *dev_find_device(u16 vendor, u16 device, struct device *from);
 struct device *dev_find_class(unsigned int class, struct device *from);