find with grep
grep -rnw '/path/to/somewhere/' -e 'pattern'
include
grep --include=\*.{c,h} -rnw '/path/to/somewhere/' -e "pattern"
exclude
grep --exclude=\*.o -rnw '/path/to/somewhere/' -e "pattern"
with dir
grep --exclude-dir={dir1,dir2,*.dst} -rnw '/path/to/somewhere/' -e "pattern"