docs(input[radio]): explain what happens with same name on multiple inputs

Closes #15009

Closes #16478

Author: gkalpak

src/ng/directive/input.js

@@ -980,6 +980,33 @@ var inputType = {
    * @description
    * HTML radio button.
    *
+   * **Note:**<br>
+   * All inputs controlled by {@link ngModel ngModel} (including those of type `radio`) will use the
+   * value of their `name` attribute to determine the property under which their
+   * {@link ngModel.NgModelController NgModelController} will be published on the parent
+   * {@link form.FormController FormController}. Thus, if you use the same `name` for multiple
+   * inputs of a form (e.g. a group of radio inputs), only _one_ `NgModelController` will be
+   * published on the parent `FormController` under that name. The rest of the controllers will
+   * continue to work as expected, but you won't be able to access them as properties on the parent
+   * `FormController`.
+   *
+   * <div class="alert alert-info">
+   *   <p>
+   *     In plain HTML forms, the `name` attribute is used to identify groups of radio inputs, so
+   *     that the browser can manage their state (checked/unchecked) based on the state of other
+   *     inputs in the same group.
+   *   </p>
+   *   <p>
+   *     In AngularJS forms, this is not necessary. The input's state will be updated based on the
+   *     value of the underlying model data.
+   *   </p>
+   * </div>
+   *
+   * <div class="alert alert-success">
+   *   If you omit the `name` attribute on a radio input, `ngModel` will automatically assign it a
+   *   unique name.
+   * </div>
+   *
    * @param {string} ngModel Assignable AngularJS expression to data-bind to.
    * @param {string} value The value to which the `ngModel` expression should be set when selected.
    *    Note that `value` only supports `string` values, i.e. the scope model needs to be a string,