[Samba] How to make samba 3 trusts samba 4

[rzavila]

Dear Sirs

in  https://lists.samba.org/archive/samba-technical/2012-August/086228.html
 Mr Andrew Bartlett
states that "Sort of. Samba3 can trust Samba4, but not the reverse"

So if PDC Domain samba 3 NT Trusts a DC Samba 4 AD , Users authenticated in
a Domain Samba 4 AD should be able to access Resources in Domain Samba 3

Could someone point me some tutorial or guide of how to do that ?

Thanks in advance

Rodrigo Zandavalli Avila