Tsong kha pa's definition of man ngag (upadeśa)

Ever wondered what those mysterious "oral teachings" are?

Are they things that are never ever revealed anywhere in writing?

Apparently not, at least that is what Tsong kha pa seems to think.

de'i phyir man ngag ni | rtsa rgyud rnams kyi don bshad rgyud kyi rjes su 'brangs nas phyin ci ma log par bshad de slob ma'i rgyud la go ba bde blag tu skyed pa'i thabs la zer bas zhal las shes lugs kyang de ltar du go bar bya yi | rgyud rnams su bri bar phangs nas de dag tu ma bkod par rna khung du rim pa bzhin brgyud pa la mi gzung ngo ||

Sngags rim chen mo (Mtsho sngon ed., p. 436)