Alternatively you can get one of these cheaper options that clip on to the vent to the right or left of the steering wheel. I use something similar in my CX-9 and it works just fine. It should also work with the vents on the CX-30, but don't quote me on that. The negative to this type of mount is that it will block air flow coming from the vent it is clipped on to.
Then there are the suction cup mounts that attach to the windshield or dashboard, like this one.
sm1ke pretty much covered everything. You just have to pick one that best suits your needs.
Personally, I despise anything mounted with suction cups. They always seem to "pop off" while you are driving and end up in your lap or on the floor.
The ProClip USA mounts are expensive but worth the money. I have used them in my 2003 Miata, 2008 Miata, 2008 3 and 2010 3. The car mount for the 2008 Miata isn't the best design so I mounted their adjustable phone holder to a Kuda car mount. The ProClip car mount for the CX-30 is a decent design though so you shouldn't have an issue with it.
I found this commercial months ago when I was looking for a possible cell phone holder for my car. It's an official accessory from Mazda. The only thing is that Australia seems to be the only one advertising this. I haven't seen any of these being sold anywhere. Not even an eBay auction or anything.