update CONTRIBUTING.md (#26764)

CONTRIBUTING.md

@@ -35,6 +35,61 @@ To contribute follow the next steps:
 The Conan Community works hard to review all the pull requests and provide assistance where need.
 The [Review Process](docs/review_process.md) is partially automated with the help of @conan-center-index-bot :rocket:
 
+## Pull Request scope
+
+Pull requests should propose changes to a single recipe only. If you believe modifications
+to multiple recipes are necessary, we kindly ask that you open an issue first to discuss
+the best approach with the maintainer team.
+
+Please ensure that pull requests have a **single**, clear objective that is evident to
+reviewers, with all proposed changes directly supporting that goal. Please refrain from
+including unrelated modifications, even if they appear minor or trivial.
+
+As the Conan client continues to evolve, we recognize that recipe conventions may change
+over time, much like in programming languages themselves. However, please be aware that it
+is not a goal in Conan Center to update all recipes to align with the latest conventions,
+as this would be an ongoing task that would consume a significant part of our resources.
+Changes of this kind will only be considered if they present tangible benefits to the
+recipe consumers -such as bug fixes or new features-, and are clearly justified in the
+pull request description. Our team will strive to upgrade recipes to the latest
+conventions as resources permit. Thank you for your understanding and cooperation.
+
+Please keep in mind that the review team is tasked with assessing a high volume of pull
+requests at any given time. To maintain an agile review process, and in accordance with
+our previous
+[announcement](https://github.com/conan-io/conan-center-index/discussions/25461), we
+kindly ask that PRs refrain from performing large-scale refactorings to eliminate Conan
+1.x compatibility, or refactoring recipe logic, unless the changes are directly related to
+the PR objective (bugfix or feature). Pull requests that include changes unrelated to the
+PR objective will not be reviewed and may be closed.
+
+## Pull Request limits
+
+The pull request workflow is constrained by our available resources, including the number
+of team reviewers and CI capacity. Given Conan Center’s large user base and its role
+within the Software Supply Chain, each pull request undergoes the same validation process
+prior to merging. Our objective is to minimize disruption for our users and prioritize
+security.
+
+To help manage the workload of the reviewing team and our CI resources, while ensuring
+that all contributors have an equitable opportunity for their pull requests to be
+reviewed, please note the following limits:
+
+- Pull requests from new contributors, or from trusted contributors after a period of
+  inactivity, need to be visually inspected by a team member before starting the CI job.
+- For trusted contributors, pull requests will automatically be checked by CI up to a
+  maximum of 30 open pull requests by the same contributor. Beyond this limit, CI runs
+  will require manual approval by the team.
+- Contributors are limited to a maximum of 50 open pull requests at any given time.
+  Additional pull requests will be closed or not reviewed until the limit is reduced. 
+
+We thank you for playing a part in prioritizing your own pull requests before opening them
+for review and CI checks. For use cases that may require modifying multiple recipes or
+extensive changes across the repository, we encourage you to first open an issue. This
+allows us to assess user interest, determine if the feature aligns with the project’s
+goals, and discuss potential implementation strategies. This helps us prioritize focusing
+on the impact proposed features have on the wider Conan Center community.
+
 ## Issues
 
 If you think you found a bug in CCI or in a recipe, open an issue indicating the following: