I want you, my boy, to do your duty in the station, whatever it may be, to which it will please God to call you.

【翻译】孩子，我希望你在车站工作要尽职尽责，不管工作是什么，召唤你做它都会让上帝高兴的。

1. 句子分两大块：

I want you, my boy, to do your duty in the station（主句）, whatever it may be, to which it will please God to call you.（让步从句）

2. 在让步从句中，又包含一个“非限制性定语从句”： to which it will please God to call you.

3. 关系代词which 指whatever，whatever 表示“任何种类的工作”，相当于any kind of work。

4. 我们把定语从句变成一个单句，就容易理解了：

it will please God to call you to any kind of work.

召唤你做任何工作都会让上帝高兴的。

to call you to any kind of work 是真实主语；it是 形式主语。

最后，重点是：句中which，指代whatever，而whatever 意思是 any kind of work。关系就是这样的。