cpp-style: Special note on acronyms

There was a discussion in code reviews on how acronyms should be
handled.  In DBus interfaces, we have used UpperCamelCase through-out
and therefore acronyms are always UPPERCASE in DBus interfaces
specifically.  There was an attempt to carry this forward into C++
style, which caused a contradiction between acronyms-always-uppercase
and variables-are-lower-case.  Clarify this to indicate that acronyms
should always be same-case and are UPPER or lower depending on the
context.

Change-Id: I5bf19595ba38405d1d5d629f8ce854bbc47af8cf
Signed-off-by: Patrick Williams <patrick@stwcx.xyz>
diff --git a/cpp-style-and-conventions.md b/cpp-style-and-conventions.md
index 442d6ef..91e8119 100644
--- a/cpp-style-and-conventions.md
+++ b/cpp-style-and-conventions.md
@@ -259,6 +259,16 @@
 ### Naming Conventions.
 
 * We generally abstain from any prefix or suffix on names.
+* Acronyms should be same-case throughout and follow the requirements as
+  in their appropriate section.
+
+```
+/// Correct.
+SomeBMCType someBMCVariable = bmcFunction();
+
+/// Wrong: type and variable are mixed-case, function isn't lowerCamelCase.
+SomeBmcType someBmcVariable = BMCFunction();
+```
 
 #### Files