I noticed that for pathfield it is mentioned with property as filter. So in that case i need to write custom filter ,could some provide sample code will be helpful.
<reference
jcr:primaryType="nt:unstructured"
sling:resourceType="granite/ui/components/coral/foundation/form/pathfield"
fieldLabel="Reference"
margin="{Boolean}true"
name="./path"
filter="nosystem"
rootPath="/content"/>