After I talked with co-author of play with topic subdomains, I was a little bit confused. My current framework doesn't support my thoughts and I was started write some code!

Application.scala

// app/controllers/Application.scala

trait SubdomainController extends Controller {
  def WithSubdomain(f: => String => Request[AnyContent] => Result) = Action { implicit request =>
    val splitDomain = request.domain.split("\\.")

    if (splitDomain.length < 2) {
      BadRequest("Domain not found!")
    } else {
      f(splitDomain.head)(request)
    }
  }
}

index.scala.html

<!-- app/views/some/index.scala.html -->

@(implicit request: play.api.mvc.Request[Any], subdomain: String)

Hi! You're on <a href="@helper.linkWithSubdomain(routes.SomeController.index)">@subdomain</a> subdomain.

Link.scala

// app/helpers/Link.scala

import play.api._
import play.api.mvc._

package views.html.helper {
  object linkWithSubdomain {
    def apply(path: play.api.mvc.Call, ssl: Boolean = false)(implicit subdomain: String, request: RequestHeader): String = {
      linkToSubdomain(subdomain = subdomain, path = path, ssl = ssl)
    }
  }

  object linkToSubdomain {
    def apply(path: play.api.mvc.Call, subdomain: String, ssl: Boolean = false)(implicit request: RequestHeader): String = {
      val schema = if (ssl) "https" else "http"

      if (request.host.split("\\.").head == subdomain)
        "%s://%s%s" format(schema, request.host, path.toString)
      else
        "%s://%s.%s%s" format(schema, subdomain, request.host, path.toString)
    }
  }
}

SomeController.scala

// app/controllers/SomeController.scala

object SomeController extends SubdomainController{
  def index = WithSubdomain { implicit domain => implicit request =>
    Domain.findByName(domain) match {
      case Some(foundDomain: Domain) =>
        Ok(views.html.some.index())
      case _ => Ok("Nothing found!")
    }
  }
}