diff --git a/docs/device_assignment.md b/docs/device_assignment.md
index 4c5b477..1166cdf 100644
--- a/docs/device_assignment.md
+++ b/docs/device_assignment.md
@@ -165,10 +165,10 @@
 ```
 
 If you compile the above with `dtc -@`, then you'll get `__symbols__` for free.
-The generated `__symbols__` indicates that there are four assignable devices.
+`__symbol__` has label of nodes, and it's required for the next step.
 
 ```dts
-    // generated __symbols__. AVF will ignore non-overlayable nodes.
+    // generated __symbols__
     __symbols__ {
         iommu0 = "/host/iommu0";
         iommu1 = "/host/iommu1";
@@ -200,10 +200,10 @@
 
 * `<kind>`: Device kind. Currently only used for debugging purposes and not used
   for device assignment.
-* `<dtbo_label>`: Label in the VM DTBO (i.e. symbols in `__symbols__`). Must be
-  unique.
+* `<dtbo_label>`: Label in the VM DTBO (i.e. symbol in `__symbols__`). Must be
+  non-empty and unique in the XML.
 * `<sysfs_path>`: Sysfs path of the device in host, used to bind to the VFIO
-  driver. Must be unique in the XML.
+  driver. Must be non-empty and unique in the XML.
 
 ## Boot with VM DTBO
 
diff --git a/pvmfw/src/device_assignment.rs b/pvmfw/src/device_assignment.rs
index b8912ce..d4f87c6 100644
--- a/pvmfw/src/device_assignment.rs
+++ b/pvmfw/src/device_assignment.rs
@@ -167,9 +167,7 @@
     //           rng { ... };      // Actual device node is here. If overlaid, path would be "/rng"
     //         };
     //       };
-    //       __symbols__ {         // List of assignable devices
-    //         // Each property describes an assigned device device information.
-    //         // property name is the device label, and property value is the path in the VM DTBO.
+    //       __symbols__ {         // Contains list of assignable devices
     //         rng = "/fragment@rng/__overlay__/rng";
     //       };
     //    };
@@ -581,10 +579,13 @@
 
         let Some(node) = fdt.node(&node_path)? else { return Ok(None) };
 
-        // Note: Currently can only assign devices backed by physical devices.
+        // Currently can only assign devices backed by physical devices.
         let phandle = dtbo_node.get_phandle()?.ok_or(DeviceAssignmentError::InvalidDtbo)?;
-        let physical_device =
-            physical_devices.get(&phandle).ok_or(DeviceAssignmentError::InvalidDtbo)?;
+        let Some(physical_device) = physical_devices.get(&phandle) else {
+            // If labeled DT node isn't backed by physical device node, then just return None.
+            // It's not an error because such node can be a dependency of assignable device nodes.
+            return Ok(None);
+        };
 
         let reg = parse_node_reg(&node)?;
         Self::validate_reg(&reg, &physical_device.reg, hypervisor)?;