resource: Introduce resource_intersection() for overlapping resources

There will be at least one user that can utilize new helper.
Provide the helper for future user and for wider use.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Reviewed-by: Hanjun Guo <guohanjun@huawei.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

include/linux/ioport.h

@@ -236,6 +236,16 @@ static inline bool resource_overlaps(struct resource *r1, struct resource *r2)
        return r1->start <= r2->end && r1->end >= r2->start;
 }
 
+static inline bool
+resource_intersection(struct resource *r1, struct resource *r2, struct resource *r)
+{
+	if (!resource_overlaps(r1, r2))
+		return false;
+	r->start = max(r1->start, r2->start);
+	r->end = min(r1->end, r2->end);
+	return true;
+}
+
 static inline bool
 resource_union(struct resource *r1, struct resource *r2, struct resource *r)
 {