Alireza,
We distinguish (vanilla) CAs from PCAs in PEM, so the name
subordination requirement that applies to subordinates of CAs, does
not apply to subordinates of PCAs. The portion of RFC 1422 you cited
refers to (vanilla) CAs, not to PCAs or to the IPRA. Thus, for
example, BBN could register as a CA under an RSA PCA but the BBN CA DN
need have no syntactic relationship to the RSA PCA DN. The precise
applicability of the DN subordination requirement is described in RFC
1422 Section 3.6.3.
Steve