The organization must define its own method. What the CMM implies is that the organization will define a method that is documented in writing. In fact, the organization should probably have more than one method to modify the process to each type of project. Software process models, such as the CMM, are much more helpful than Highsmith would have us believe. Some organizations may misuse them, but the goals of these models are hardly overly restrictive.
Software processes are frameworks to organize our work.
And because software development techniques evolve, the process must be improved to follow the organization environment changes.