diff --git a/newsfragments/3221.doc.rst b/newsfragments/3221.doc.rst
new file mode 100644
index 0000000000..f90aca8094
--- /dev/null
+++ b/newsfragments/3221.doc.rst
@@ -0,0 +1 @@
+Added docstrings for :attr:`~trio.lowlevel.ParkingLot.broken_by` and :meth:`~trio._subprocess.HasFileno.fileno`.
diff --git a/src/trio/_core/_parking_lot.py b/src/trio/_core/_parking_lot.py
index ddf6276117..c44661b5f5 100644
--- a/src/trio/_core/_parking_lot.py
+++ b/src/trio/_core/_parking_lot.py
@@ -152,6 +152,7 @@ class ParkingLot:
     # items
     _parked: OrderedDict[Task, None] = attrs.field(factory=OrderedDict, init=False)
     broken_by: list[Task] = attrs.field(factory=list, init=False)
+    """The list of tasks that have broken this lot via :meth:`break_lot`."""
 
     def __len__(self) -> int:
         """Returns the number of parked tasks."""
diff --git a/src/trio/_subprocess.py b/src/trio/_subprocess.py
index d73ba3dc23..33197e9ac8 100644
--- a/src/trio/_subprocess.py
+++ b/src/trio/_subprocess.py
@@ -98,7 +98,9 @@ def pidfd_open(fd: int, flags: int) -> int:
 class HasFileno(Protocol):
     """Represents any file-like object that has a file descriptor."""
 
-    def fileno(self) -> int: ...
+    def fileno(self) -> int:
+        """Return the underlying file descriptor as an integer."""
+        ...
 
 
 @final
diff --git a/src/trio/_tests/_check_type_completeness.json b/src/trio/_tests/_check_type_completeness.json
index e5414cfe56..309b4e13f3 100644
--- a/src/trio/_tests/_check_type_completeness.json
+++ b/src/trio/_tests/_check_type_completeness.json
@@ -25,7 +25,6 @@
         "No docstring found for function \"trio._highlevel_socket.SocketStream.send_eof\"",
         "No docstring found for function \"trio._highlevel_socket.SocketStream.receive_some\"",
         "No docstring found for function \"trio._highlevel_socket.SocketStream.aclose\"",
-        "No docstring found for function \"trio._subprocess.HasFileno.fileno\"",
         "No docstring found for class \"trio._sync.AsyncContextManagerMixin\"",
         "No docstring found for function \"trio._sync._HasAcquireRelease.acquire\"",
         "No docstring found for function \"trio._sync._HasAcquireRelease.release\"",