Making this restfull

Hi, i am having great difficulties making my app restfull.

this is the case:
i have organisations and organisationtypes
all organisations belong to a certain type.
the organisationtypes are not pre-determined, so making a controller for
each organisationtype is not possible

what would be the best way to get a list of organisations of a certain
type, lets say customers?

is the url below considered restfull?
/organisations?type=customer

or should I make an extra controller like organisationtypelists and do:

/organisationtypelist/customer

in that case i would end up with three controllers: organisations,
organisationtypes and organisationstypelists

or are there better ways?

i see a lot of different opinions on this, so i don’t know what is best