This a design of one of the downlight that my company manufactures. But obviously some of the components has been removed so that it looks pretty much common. So if you are using it you will need to add the details for the fastners , lamp holders, cable entry and diffuser.

Legends:
Red -> Control gear case-
White-> Bracket to hold the diffuser and reflector
Green-> Base plate
Glolden -> Bracket for Diffuser.

So one still needs to find out the size of clips/spring that will be connected to 'White' on the sides to support the 'Golden'. Now these vary depending upon the requirement. Base plate is optional, in most of the designs, the 'Red' houses the control gear is sufficient and there is no need to provide a joint to red and white. This design for downlight is needed for special kind of false ceilings.

Alls well that ends well.