Haven't buy any cam yet, just like to know if I buy certain brand, would I be restricted only to certain lense brand.
You are restricted in:
a) you need to have the right mount type for your camera system. Mount here means: mechanical mount (Bayonet, Screw type etc.) and electrical mount (contacts, communication with camera). Mechanical mount is a must, electrical mount is optional.
If you have Canon then it would be most useful to get lenses with Canon mount (Canon calls it EF mount for "Electronic Focus"). Many third party lens manufacturers offer their lenses with Canon EF mounts (Tamron, Sigma, Tokina) in full function, the lenses work in the same way as any Canon lens. This is the hassle-free solution for people who just want to use a 3rd party lens lens of a certain brand / focal length.
Some third party lenses are full manual lenses, e.g. Carl Zeiss (just released) and some Russian lenses (Zenitar). You can mount these lenses on your camera but you must set aperture and focus manually.
b) you need to have the right adapter.
There are a couple of adapters to mount lenses across the systems, e.g. a lens with Konica/Minolta mount to a Canon camera. Pure mechanical adapters allow you to mount the lens but the camera cannot adjust the aperture or focus. You need to do that manually, provided the lens has the respective setting rings. Check this first, most lenses have manual focus ring but not all have aperture ring.
There are some adapters with a chip for AF confirmation. This means: when you focus manually the camera can notice when the best focus is achieved and you'll get a confirmation in the same way as in Automatic Focus. It's a good support to achieve focus.
Not a restriction but rather learning is the handling of such lenses with adapters. Since the auto focus / auto aperture doesn't work you need to do some things manually. Focus is easier but metering can be tricky.
Personally I'd recommend you staying with option a) first. The equipment sections here in the forum have price lists for 3rd party lenses that give a good overview about the availble range of lenses. In addition you can the web sites of the vendors, they will list which mounts are available for certain lenses.
