angularjs 双向数据绑定问题

做一个app样式的搜索功能，默认页面列出所有内容，根据搜索框内容筛选显示符合条件的项目，
搜索框放在ion-nav-title中就不在一个controller里了，这样怎么实现搜索框内容改变，主页内容中跟着变化？

html：
<ion-view ng-controller="PlaylistsCtrl" class="app_android" hide-nav-bar="false">
    <ion-nav-title>
        <div class="search-wrap" ng-controller="searchInput">
            <div class="search" style="width: 100%;">
                <label class="item-input">
                    <i class="icon ion-ios-search-strong placeholder-ion"></i>
                    <input type="search" placeholder="Find Doctor, Clinics, Specialist" ng-model="searchInput" ng-change="change(searchInput);">
                </label>
            </div>
        </div>
    </ion-nav-title>
    <ion-content class="app_find" overflow-scroll="false">
        <ion-refresher on-refresh="doRefresh();" refreshing-icon="ion-ios-eye-outline">
        </ion-refresher>
        <ion-list>
            <ion-item ng-repeat="playlist in playlists | filter:{title:searchInput}">
            </ion-item>
        </ion-list>
    </ion-content>
</ion-view>