class MainModuleServiceProvider extends ServiceProvider
{
    public function register()
    {
        $this->app->register( FirstModuleServiceProvider::class );
        $this->app->register( SecondModuleServiceProvider::class );
    }
}

class FirstModuleServiceProvider extends ServiceProvider
{
    public function register()
    {
        $this->app->register( RouteServiceProvider::class );
        $this->app->register( ViewServiceProvider::class );
    }
}