Highly quick-and-dirty:

  $ git log origin/release_37..origin/release_38 --no-merges -i --grep \
    'ppc\|power pc' --pretty='%ae' | grep --only-matching '@.*' | sort | \
    uniq -c | sort -rn
       16 @anl.gov
       11 @gmail.com
	7 @linux.vnet.ibm.com
	4 @iteratee.net
	3 @ca.ibm.com
	2 @hanshq.net
	2 @de.ibm.com
	2 @apple.com
	1 @samsung.com
	1 @linaro.org
	1 @imgtec.com
	1 @googlemail.com
	1 @codeaurora.org

You'd have to look at the individual addresses to disambiguate who @gmail.com and @googlemail.com are; at least 5 are from a Googler. @iteratee.net is also a Googler.