[PATCH] docs/misra/rules.rst: allow string literals with memcmp

[Stefano Stabellini <sstabellini@xxxxxxxxxx>]

Rule 21.16 is about the types of arguments allowed for memcpy. Add
string literals to the allow-list under specific conditions.

Suggested-by: Jan Beulich <jbeulich@xxxxxxxx>
Signed-off-by: Stefano Stabellini <stefano.stabellini@xxxxxxx>

diff --git a/docs/misra/rules.rst b/docs/misra/rules.rst
index e1c26030e8..3e014a6298 100644
--- a/docs/misra/rules.rst
+++ b/docs/misra/rules.rst
@@ -813,7 +813,9 @@ maintainers if you want to suggest a change.
        shall point to either a pointer type, an essentially signed type,
        an essentially unsigned type, an essentially Boolean type or an
        essentially enum type
-     - void* arguments are allowed
+     - void* arguments are allowed. string literal arguments are allowed
+       when the last argument passed for the comparison is less or equal
+       to the size of the string.
 
    * - `Rule 21.17 
<https://gitlab.com/MISRA/MISRA-C/MISRA-C-2012/Example-Suite/-/blob/master/R_21_17.c>`_
      - Mandatory