How to call function of one controller from another controller

Function of one (first) SAPUI5 view controller can be called from another (second) SAPUI5 view controller –

if this function is subscribed to some event of EventBus in the first controller:

onInit: function() {
    sap.ui.getCore().getEventBus().subscribe(
        "SomeChannel",
        "SomeEvent",
        this.someFunctionOfTheFirstController,
        this
    );
},
someFunctionOfTheFirstController: function (sChannelId, sEventId, sData) {
    console.log(
        "Function of the first controller " + sData
    );
}

and the same event of EventBus is published in the second controller:

functionOfTheSecondController: function () {
    sap.ui.getCore().getEventBus().publish(
        "SomeChannel",
        "SomeEvent",
        "is called from function of the second controller."
    );
}