gistfile1.txt

19:58 < happytux> I do this because I want that the role  'role::mail::primary' will be looked up as mail_primary.yaml.

see files...

gistfile2.txt

as fact or in site.pp or via an ENC or whatever method set $role and $subrol for a node

gistfile3.txt

in the following hierarchy

/etc/puppet/hieradata/mail/primary.yaml
/etc/puppet/hieradata/mail/secondary.yaml
/etc/puppet/hieradata/mail/common.yaml
/etc/puppet/hieradata/<otherrole>/common.yaml

hiera.yaml

---
:hierarchy:
  - 01_nodes/%{::fqdn}
  - 01_nodes/%{::hostname}
  - 02_roles/%{::role}/${::subrole}
  - 02_roles/%{::role}/common
  - common

:yaml:
  :datadir: /etc/puppet/hieradata

mail-common.yaml

---
classes:
 - <class common to all mail subroles>

mail-primary.yaml

---
classes:
  - postfix
  - <someclass>

site.pp

# This will combine the array of all the classes in the matching yaml files in the hierarchy.

hiera_include("classes", [] )