Gradle custom task type defined in buildSrc not accessible in subprojects for multi-project structure

I have a gradle multi-project hierarchy:

root
-buildSrc
 -src/main/groovy/com/CustomTask.groovy
-subproj1
-subproj1
-build.gradle
-settings.gradle

I am able to invoke custom task - com.CustomTask only from root build.gradle file but I get - Unable to resolve class CustomTask at line import com.CustomTask when called from subproj1/build.gradle

import com.CustomTask

task customTask(type: CustomTask) {
        setModuleRoot(project.projectDir)
    }

Can anyone please suggest me how can I invoke a custom task defined under root level buildSrc from subproject's build.gradle file? (I am on gradle Gradle 7.1.1 version)