Attachment order of scsibus*

[Edgar Fuß <ef%math.uni-bonn.de@localhost>]

I had only one SCSI controller, an mpt(4), so scsibus0 at mpt0 and 
sd0/1 at scsibus0.

Now, I have an additional mpii(4), and mpii0 attaches before mpt0 
(despite the order in config being the other way round) and I get
scsibus0 at mpii0 and scsibus1 at mpt0, thus my former sd0/1 become 
sdn/n+1, with n being the number of drives attached to mpii0/scsibus0.

Is there a way to steer the order of attachments?