Some doc formatting and link, mostly on quantumcircuit.py file

qiskit/circuit/bit.py

@@ -19,7 +19,13 @@
 
 
 class Bit:
-    """Implement a generic bit."""
+    """Implement a generic bit.
+
+    .. note::
+        This class should be instantiated directly, but just a super class
+        for :class:`~.Clbit` and :class:`~.Qubit`.
+
+    """
 
     __slots__ = {"_register", "_index", "_hash", "_repr"}
 

qiskit/circuit/register.py

@@ -38,7 +38,13 @@ def __get__(self, obj, objtype=None):
 
 
 class Register:
-    """Implement a generic register."""
+    """Implement a generic register.
+
+    .. note::
+        This class should be instantiated directly, but just a super class
+        for :class:`~.ClassicalRegister` and :class:`~.QuantumRegister`.
+
+    """
 
     __slots__ = ["_name", "_size", "_bits", "_bit_indices", "_hash", "_repr"]