Answer by Marco A. for Where is the definition of `top-level cv-qualifiers` in the C++11 Standard?

From Dan Saks's Top-Level cv-Qualifiers in Function Parameters:

In C++, a cv-qualifier that applies to the first level of a type is called a toplevel cv-qualifier. For example, in:

T *const p;

the top-level cv-qualifier is const, and in:

T const *volatile q;

the top-level cv-qualifier is volatile. On the other hand:

T const volatile *q;

has no top-level cv-qualifiers. In this case, the cv-qualifiers const and volatile appear at the second level.

The signature of a function includes all cv-qualifiers appearing in that function’s parameter types, except for those qualifiers appearing at the top-level of a parameter type.

For example, in:

int f(char const *p);

the const qualifier is not at the top level in the parameter declaration, so it is part of the function’s signature.

On the other hand, in:

int f(char *const p);

the const qualifier is at the top level, so it is not part of the function’s signature. This function has the same signature as:

int f(char *p);

I couldn't find a definition in the standard either but what I posted above is explicitly stated in N3337 §8.3.5-5

After producing the list of parameter types, any top-levelcv-qualifiers modifying a parameter type are deleted when forming thefunction type.

Edit:At the time of writing the above post a definition in the standard could not be found but now there's one as pointed out by Shafik:

n4296 excerpt:

In this International Standard, the notation cv (or cv1 , cv2 , etc.),used in the description of types, represents an arbitrary set ofcv-qualifiers, i.e., one of {const}, {volatile}, {const, volatile}, orthe empty set. For a type cv T, the top-level cv-qualifiers of thattype are those denoted by cv. [Example: The type corresponding to thetype-id const int& has no top-level cv-qualifiers. The typecorresponding to the typeid volatile int * const has the top-levelcv-qualifier const. For a class type C, the type corresponding to thetype-id void (C::* volatile)(int) const has the top-level cv-qualifiervolatile. — end example ]

In C++20 draft, N4713, the definition is found in §6.7.3 (5) ("CV-qualifiers" or [basic.type.qualifier])