rust: device: implement FwNode::is_of_node()

Implement FwNode::is_of_node() in order to check whether a FwNode
instance is embedded in a struct device_node.

Reviewed-by: Rob Herring (Arm) <robh@kernel.org>
Signed-off-by: Igor Korotin <igor.korotin.linux@gmail.com>
Link: https://lore.kernel.org/r/20250620151504.278766-1-igor.korotin.linux@gmail.com
Signed-off-by: Danilo Krummrich <dakr@kernel.org>

MAINTAINERS

@@ -18580,6 +18580,7 @@ T:	git git://git.kernel.org/pub/scm/linux/kernel/git/robh/linux.git
 F:	Documentation/ABI/testing/sysfs-firmware-ofw
 F:	drivers/of/
 F:	include/linux/of*.h
+F:	rust/helpers/of.c
 F:	rust/kernel/of.rs
 F:	scripts/dtc/
 F:	tools/testing/selftests/dt/

rust/helpers/helpers.c

@@ -28,6 +28,7 @@
 #include "kunit.c"
 #include "mm.c"
 #include "mutex.c"
+#include "of.c"
 #include "page.c"
 #include "platform.c"
 #include "pci.c"

rust/helpers/of.c

@@ -0,0 +1,8 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include <linux/of.h>
+
+bool rust_helper_is_of_node(const struct fwnode_handle *fwnode)
+{
+	return is_of_node(fwnode);
+}

rust/kernel/device/property.rs

@@ -61,6 +61,13 @@ impl FwNode {
         self.0.get()
     }
 
+    /// Returns `true` if `&self` is an OF node, `false` otherwise.
+    pub fn is_of_node(&self) -> bool {
+        // SAFETY: The type invariant of `Self` guarantees that `self.as_raw() is a pointer to a
+        // valid `struct fwnode_handle`.
+        unsafe { bindings::is_of_node(self.as_raw()) }
+    }
+
     /// Returns an object that implements [`Display`](core::fmt::Display) for
     /// printing the name of a node.
     ///