[PATCH] build: announce requirement for C11

[Bruce Richardson]

Add a deprecation notice informing users that we will require a C11
compiler from 23.11 release onwards. This requirement was agreed by
technical board to enable use of newer C language features, e.g.
standard atomics. [1]

[1] http://inbox.dpdk.org/dev/DBAPR08MB58148CEC3E1454E8848A938998AB9@DBAPR08MB5814.eurprd08.prod.outlook.com/

Signed-off-by: Bruce Richardson <bruce.richardson at intel.com>
---
 doc/guides/rel_notes/deprecation.rst | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/doc/guides/rel_notes/deprecation.rst b/doc/guides/rel_notes/deprecation.rst
index dcc1ca1696..9a391d2c49 100644
--- a/doc/guides/rel_notes/deprecation.rst
+++ b/doc/guides/rel_notes/deprecation.rst
@@ -11,6 +11,12 @@ here.
 Deprecation Notices
 -------------------
 
+* C Compiler: From DPDK 23.11 onwards,
+  building DPDK will require a C compiler which supports the C11 standard, or later.
+  Please note:
+     - C11 is supported from GCC version 5 onwards, and is the default language version in that release
+     - C11 is the default compilation mode in Clang from version 3.6
+
 * kvargs: The function ``rte_kvargs_process`` will get a new parameter
   for returning key match count. It will ease handling of no-match case.
 
-- 
2.39.2