I have given your question some thought in the last few days.
12.5 MPa is much greater than the bearing capacity of any granular soils (12.5 MPa= 260,000psf - approx., according to my Mathcad calc) I know of. This value is orders of magnitude greater than the highest values of soil bearing capacity I have ever seen, because it is rock, and not soil.
I am sure that the bearing capacity of the rock at your project site, which has a UCS of 12.5MPa, is NOT an issue for bearing capacity failure unless your loads on the footings are astronomical and / or concentrated in a very small area, which would likely require a deep foundation type design, which you indicated wasn't the case since the rock was close to the surface.
If I were designing the footings for your project, I would take the UCS, apply a safety factor of about 2.0, and call that qu or qall, and design my footings using the required ACI method, using the modified UCS as the allowable bearing capacity. I might even eliminate the footings, and anchor the column pedestals or foundation walls directly to the rock using drilled and grouted dowels.
I have used this approach in the past with great success, but I have no idea of the nature of your project, and cannot comment on it's applicability. That's an engineering decision you will have to make, and is your prerogative as the design engineer, Geotechnical or Structural, supported with calcs and assumptions of coarse.
I am still looking for an applicable equation to determine qu from the UCS of rock. I have found it to be a rarely, if ever used calculation in the design of shallow foundations since it isn't an issue for bearing capacity failure depending on the type and condition of the rock.