The new subentry password policies map 1:1 to the server config password policies. The LDAP attribute names are like the config property names prefixed with ds-pwp-.
As a first approximation, I've copied password policy reference documentation from the config ref into the chapter on password policies.
A generated password policy config ref would be better, because it would stay in sync with the code.
It might be nice to wait until the Rest2ldap configuration for password policies is ready, and that reference could also then be generated rather than written and maintained by hand.