how to get a pointer to the subarray of a 2d dynamic array?

See more:

C++

I have a two-dimensional dynamic array:

int **p=new int*[d1];
for(size_t i=0;i!=d1;++i)
  p[i]=new int[d2];

Now I need a subarray of it, like

int **b=&p[1][1]

(Of course this is not correct)
Then I could operate a block of p using b, such as
b[0][0]=10 is the same as p[1][1]=10,
b[2][3]=20 is the same as p[3][4]=20.
The question is:
How to construct such a pointer to the subarray of p?
Thank you!