Help with draconic heritage

[Kaleph]

I vaguely remember some optional rule that allowed to get draconic heritage as a bonus feat under some conditions (specific race/background/class combination) - but I'm not able to find it, and I am afraid I am mistaken and confusing it with the chance of getting dragontouched for free by being a DFA (which is a completely different thing). Can someone clarify my doubt? Thank you in advance...