diff --git a/include/zephyr/sys/sys_io.h b/include/zephyr/sys/sys_io.h
index fc3c1205d6185..ae2692764c263 100644
--- a/include/zephyr/sys/sys_io.h
+++ b/include/zephyr/sys/sys_io.h
@@ -285,7 +285,8 @@ typedef uintptr_t mem_addr_t;
  * @param addr the memory address from where to look for the bit
  * @param bit the designated bit to test (from 0 to 31)
  *
- * @return 1 if it is set, 0 otherwise
+ * @return the bitwise AND result of @p addr content and (1 << @p bit).
+ * Result is 0 only if the bit is cleared otherwise result is a non-0 value.
  */
 
 /**
@@ -298,7 +299,8 @@ typedef uintptr_t mem_addr_t;
  * @param addr the memory address from where to look for the bit
  * @param bit the designated bit to test and set (from 0 to 31)
  *
- * @return 1 if it was set, 0 otherwise
+ * @return the bitwise AND result of @p addr content and (1 << @p bit) before target bit
+ * is set. Result is 0 only if the bit was cleared otherwise result is a non-0 value.
  */
 
 /**
@@ -311,7 +313,8 @@ typedef uintptr_t mem_addr_t;
  * @param addr the memory address from where to look for the bit
  * @param bit the designated bit to test and clear (from 0 to 31)
  *
- * @return 0 if it was clear, 1 otherwise
+ * @return the bitwise AND result of @p addr content and (1 << @p bit) before target bit
+ * is cleared. Result is 0 only if the bit was cleared otherwise result is a non-0 value.
  */
 
 /**
@@ -344,7 +347,8 @@ typedef uintptr_t mem_addr_t;
  * @param addr the memory address from where to look for the bit
  * @param bit the designated bit to test (arbitrary
  *
- * @return 1 if it is set, 0 otherwise
+ * @return the bitwise AND result of @p addr content and (1 << @p bit). Result is 0
+ * only if the bit is cleared otherwise result is a non-0 value.
  */
 
 /**
@@ -357,7 +361,8 @@ typedef uintptr_t mem_addr_t;
  * @param addr the memory address from where to look for the bit
  * @param bit the designated bit to test and set (arbitrary)
  *
- * @return 1 if it was set, 0 otherwise
+ * @return the bitwise AND result of @p addr content and (1 << @p bit) before target bit
+ * is set. Result is 0 only if the bit was cleared otherwise result is a non-0 value.
  */
 
 /**
@@ -370,7 +375,8 @@ typedef uintptr_t mem_addr_t;
  * @param addr the memory address from where to look for the bit
  * @param bit the designated bit to test and clear (arbitrary)
  *
- * @return 0 if it was clear, 1 otherwise
+ * @return the bitwise AND result of @p addr content and (1 << @p bit) before target bit
+ * is cleared. Result is 0 only if the bit was cleared otherwise result is a non-0 value.
  */