AFAIK, this "mixed-endian" format is only used on little endian ARM 
(old-ABI only). 

That is true that IEEE 754 does not specify any format. I used the big 
and little endian code as a template to add the "ARM format", hence 
IEEE in the name. "mixed-endian" is the term usually used to describe 
this format in the ARM community. I am not opposed to any other name.

OTOH, if you consider that IEEE does not specify any format, "IEEE, 
little-endian" and "IEEE, big-endian" are also not correct.