top.sls

  '*':
    - test.c
    - test.d

test/a.sls :

titi:
  - toto: {{ var1 }}

test/c.sls :

include:
  - test.a:
      defaults:
          var1: toto

test/d.sls:
include:
  - test.a:
      defaults:
          var1: tata

resulting pillar.items
    titi:
        |_
          ----------
          toto:
              toto